diff --git a/.vscode/page.code-snippets b/.vscode/page.code-snippets
index c6188878..4668b0b5 100644
--- a/.vscode/page.code-snippets
+++ b/.vscode/page.code-snippets
@@ -30,21 +30,21 @@
 		"body": [
 			"import 'package:flutter/material.dart';",
 			"import 'package:flutter_hooks/flutter_hooks.dart';",
+			"import 'package:themes/themes.dart';",
 			"",
-			"import '../../../../commons/hooks/hooks.dart';",
-			"import '../../../style/style.dart';",
+			"import '../../../gen/strings.g.dart';",
 			"",
 			"class ${TM_FILENAME_BASE/(.*)/${1:/pascalcase}${2}/} extends HookWidget implements PreferredSizeWidget {",
 			"  const ${TM_FILENAME_BASE/(.*)/${1:/pascalcase}${2}/}({super.key});",
 			"",
 			"  @override",
-			"  Size get preferredSize => appbarSize;",
+			"  Size get preferredSize => appBarDefaultSize;",
 			"",
 			"  @override",
 			"  Widget build(BuildContext context) {",
-			"    final l10n = useL10n();",
+			"    final t = Translations.of(context);",
 			"    return AppBar(",
-			"      title: Text(l10n.${TM_FILENAME_BASE/(.*)/${1:/camelcase}${2}/}Title),",
+			"      title: Text(t.${TM_FILENAME_BASE/[\\._]/./g}.title),",
 			"    );",
 			"  }",
 			"}",
@@ -67,7 +67,7 @@
 			"",
 			"  @override",
 			"  Widget build(BuildContext context, WidgetRef ref) {",
-			"    final l10n = useL10n();",
+			"    final t = Translations.of(context);",
 			"    return $1;",
 			"  }",
 			"}",
diff --git a/melos.yaml b/melos.yaml
index 64cf5f0a..bb907dd7 100644
--- a/melos.yaml
+++ b/melos.yaml
@@ -8,9 +8,6 @@ packages:
 command:
   bootstrap:
     runPubGetInParallel: true
-    hooks:
-      post: |
-        melos exec --flutter --dir-exists=lib/l10n -- "flutter gen-l10n"
   clean:
     hooks:
       post: |
@@ -75,10 +72,11 @@ scripts:
       flutter: true
       dirExists: [lib, test]
 
+  # ファイル除外機能に関するissue　https://github.com/dart-lang/dart_style/issues/864
   format:ci:
     run: |
       melos exec -- \
-        dart format --set-exit-if-changed lib test
+        dart format --set-exit-if-changed $(find . -name "*.dart" -not \( -name "*.*freezed.dart" -o -name "*.*g.dart" -o -name "*.gen.dart" -o -wholename "./.dart_tool/*" \) )
     description: Run format.
     packageFilters:
       flutter: true
diff --git a/packages/flutter_app/README.md b/packages/flutter_app/README.md
index ce565419..7a9ba03b 100644
--- a/packages/flutter_app/README.md
+++ b/packages/flutter_app/README.md
@@ -34,8 +34,27 @@ Required only `--release` mode.
 
 ## How to use
 ### Localizations
+JSONファイルを作成
+```json
+{
+  "hello": "Hello $name",
+  "save": "Save",
+  "login": {
+    "success": "Logged in successfully",
+    "fail": "Logged in failed"
+  }
+}
+```
+Dartファイルを生成
+```shell
+dart run slang
+```
+
+生成されたDartファイルをimportして使用
 ```dart
-final l10n = L10n.of(context);
+import '../../../gen/strings.g.dart';
+
+final t = Translations.of(context);
 ```
 
 ## FlutterFire Configure
diff --git a/packages/flutter_app/analysis_options.yaml b/packages/flutter_app/analysis_options.yaml
index f48362f5..f3ebe017 100644
--- a/packages/flutter_app/analysis_options.yaml
+++ b/packages/flutter_app/analysis_options.yaml
@@ -3,6 +3,5 @@ analyzer:
   plugins:
     - custom_lint
   exclude:
-    - "**/l10n/*.dart"
     - "**/gen/*.dart"
     - "**/firebase_options_*.dart"
diff --git a/packages/flutter_app/l10n.yaml b/packages/flutter_app/l10n.yaml
deleted file mode 100644
index eff7e600..00000000
--- a/packages/flutter_app/l10n.yaml
+++ /dev/null
@@ -1,4 +0,0 @@
-# https://docs.flutter.dev/development/accessibility-and-localization/internationalization
-arb-dir: lib/l10n
-template-arb-file: app_en.arb
-output-localization-file: app_localizations.dart
diff --git a/packages/flutter_app/lib/features/theme_selector/theme_mode_ext.dart b/packages/flutter_app/lib/features/theme_selector/theme_mode_ext.dart
index 7c1fc242..8638d1a2 100644
--- a/packages/flutter_app/lib/features/theme_selector/theme_mode_ext.dart
+++ b/packages/flutter_app/lib/features/theme_selector/theme_mode_ext.dart
@@ -1,26 +1,27 @@
 import 'package:flutter/material.dart';
-import 'package:flutter_gen/gen_l10n/app_localizations.dart';
+
+import '../../gen/strings.g.dart';
 
 extension ThemeModeExt on ThemeMode {
-  String title(AppLocalizations l10n) {
+  String title(Translations t) {
     switch (this) {
       case ThemeMode.system:
-        return l10n.themeModeTitleSystem;
+        return t.theme.mode.title.system;
       case ThemeMode.light:
-        return l10n.themeModeTitleLight;
+        return t.theme.mode.title.light;
       case ThemeMode.dark:
-        return l10n.themeModeTitleDark;
+        return t.theme.mode.title.dark;
     }
   }
 
-  String subtitle(AppLocalizations l10n) {
+  String subtitle(Translations t) {
     switch (this) {
       case ThemeMode.system:
-        return l10n.themeModeSubtitleSystem;
+        return t.theme.mode.subtitle.system;
       case ThemeMode.light:
-        return l10n.themeModeSubtitleLight;
+        return t.theme.mode.subtitle.light;
       case ThemeMode.dark:
-        return l10n.themeModeSubtitleDark;
+        return t.theme.mode.subtitle.dark;
     }
   }
 
diff --git a/packages/flutter_app/lib/flutter_app.dart b/packages/flutter_app/lib/flutter_app.dart
index 95dc9415..83a78255 100644
--- a/packages/flutter_app/lib/flutter_app.dart
+++ b/packages/flutter_app/lib/flutter_app.dart
@@ -1,11 +1,11 @@
 import 'package:flutter/material.dart';
-import 'package:flutter_gen/gen_l10n/app_localizations.dart';
+import 'package:flutter_localizations/flutter_localizations.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:themes/themes.dart';
 
 import 'features/theme_selector/theme_selector.dart';
+import 'gen/strings.g.dart';
 import 'router/router.dart';
-import 'util/localizer/localizer.dart';
 import 'util/providers/scaffold_messenger_key_provider.dart';
 
 class FlutterApp extends ConsumerWidget {
@@ -17,12 +17,12 @@ class FlutterApp extends ConsumerWidget {
 
     return MaterialApp.router(
       routerConfig: router,
-      onGenerateTitle: (context) => L10n.of(context).title,
+      onGenerateTitle: (context) => Translations.of(context).title,
       theme: appLightThemeData,
       darkTheme: appDarkThemeData,
       themeMode: ref.watch(themeSelectorProvider),
-      localizationsDelegates: AppLocalizations.localizationsDelegates,
-      supportedLocales: AppLocalizations.supportedLocales,
+      localizationsDelegates: GlobalMaterialLocalizations.delegates,
+      supportedLocales: AppLocaleUtils.supportedLocales,
       scaffoldMessengerKey: ref.watch(scaffoldMessengerKeyProvider),
     );
   }
diff --git a/packages/flutter_app/lib/gen/strings.g.dart b/packages/flutter_app/lib/gen/strings.g.dart
new file mode 100644
index 00000000..ef4e1241
--- /dev/null
+++ b/packages/flutter_app/lib/gen/strings.g.dart
@@ -0,0 +1,940 @@
+/// Generated file. Do not edit.
+///
+/// Original: lib/i18n
+/// To regenerate, run: `dart run slang`
+///
+/// Locales: 2
+/// Strings: 52 (26 per locale)
+///
+/// Built on 2023-12-14 at 08:17 UTC
+
+// coverage:ignore-file
+// ignore_for_file: type=lint
+
+import 'package:flutter/widgets.dart';
+import 'package:slang/builder/model/node.dart';
+import 'package:slang_flutter/slang_flutter.dart';
+export 'package:slang_flutter/slang_flutter.dart';
+
+const AppLocale _baseLocale = AppLocale.ja;
+
+/// Supported locales, see extension methods below.
+///
+/// Usage:
+/// - LocaleSettings.setLocale(AppLocale.ja) // set locale
+/// - Locale locale = AppLocale.ja.flutterLocale // get flutter locale from enum
+/// - if (LocaleSettings.currentLocale == AppLocale.ja) // locale check
+enum AppLocale with BaseAppLocale<AppLocale, Translations> {
+	ja(languageCode: 'ja', build: Translations.build),
+	en(languageCode: 'en', build: _StringsEn.build);
+
+	const AppLocale({required this.languageCode, this.scriptCode, this.countryCode, required this.build}); // ignore: unused_element
+
+	@override final String languageCode;
+	@override final String? scriptCode;
+	@override final String? countryCode;
+	@override final TranslationBuilder<AppLocale, Translations> build;
+
+	/// Gets current instance managed by [LocaleSettings].
+	Translations get translations => LocaleSettings.instance.translationMap[this]!;
+}
+
+/// Method A: Simple
+///
+/// No rebuild after locale change.
+/// Translation happens during initialization of the widget (call of t).
+/// Configurable via 'translate_var'.
+///
+/// Usage:
+/// String a = t.someKey.anotherKey;
+/// String b = t['someKey.anotherKey']; // Only for edge cases!
+Translations get t => LocaleSettings.instance.currentTranslations;
+
+/// Method B: Advanced
+///
+/// All widgets using this method will trigger a rebuild when locale changes.
+/// Use this if you have e.g. a settings page where the user can select the locale during runtime.
+///
+/// Step 1:
+/// wrap your App with
+/// TranslationProvider(
+/// 	child: MyApp()
+/// );
+///
+/// Step 2:
+/// final t = Translations.of(context); // Get t variable.
+/// String a = t.someKey.anotherKey; // Use t variable.
+/// String b = t['someKey.anotherKey']; // Only for edge cases!
+class TranslationProvider extends BaseTranslationProvider<AppLocale, Translations> {
+	TranslationProvider({required super.child}) : super(settings: LocaleSettings.instance);
+
+	static InheritedLocaleData<AppLocale, Translations> of(BuildContext context) => InheritedLocaleData.of<AppLocale, Translations>(context);
+}
+
+/// Method B shorthand via [BuildContext] extension method.
+/// Configurable via 'translate_var'.
+///
+/// Usage (e.g. in a widget's build method):
+/// context.t.someKey.anotherKey
+extension BuildContextTranslationsExtension on BuildContext {
+	Translations get t => TranslationProvider.of(this).translations;
+}
+
+/// Manages all translation instances and the current locale
+class LocaleSettings extends BaseFlutterLocaleSettings<AppLocale, Translations> {
+	LocaleSettings._() : super(utils: AppLocaleUtils.instance);
+
+	static final instance = LocaleSettings._();
+
+	// static aliases (checkout base methods for documentation)
+	static AppLocale get currentLocale => instance.currentLocale;
+	static Stream<AppLocale> getLocaleStream() => instance.getLocaleStream();
+	static AppLocale setLocale(AppLocale locale, {bool? listenToDeviceLocale = false}) => instance.setLocale(locale, listenToDeviceLocale: listenToDeviceLocale);
+	static AppLocale setLocaleRaw(String rawLocale, {bool? listenToDeviceLocale = false}) => instance.setLocaleRaw(rawLocale, listenToDeviceLocale: listenToDeviceLocale);
+	static AppLocale useDeviceLocale() => instance.useDeviceLocale();
+	@Deprecated('Use [AppLocaleUtils.supportedLocales]') static List<Locale> get supportedLocales => instance.supportedLocales;
+	@Deprecated('Use [AppLocaleUtils.supportedLocalesRaw]') static List<String> get supportedLocalesRaw => instance.supportedLocalesRaw;
+	static void setPluralResolver({String? language, AppLocale? locale, PluralResolver? cardinalResolver, PluralResolver? ordinalResolver}) => instance.setPluralResolver(
+		language: language,
+		locale: locale,
+		cardinalResolver: cardinalResolver,
+		ordinalResolver: ordinalResolver,
+	);
+}
+
+/// Provides utility functions without any side effects.
+class AppLocaleUtils extends BaseAppLocaleUtils<AppLocale, Translations> {
+	AppLocaleUtils._() : super(baseLocale: _baseLocale, locales: AppLocale.values);
+
+	static final instance = AppLocaleUtils._();
+
+	// static aliases (checkout base methods for documentation)
+	static AppLocale parse(String rawLocale) => instance.parse(rawLocale);
+	static AppLocale parseLocaleParts({required String languageCode, String? scriptCode, String? countryCode}) => instance.parseLocaleParts(languageCode: languageCode, scriptCode: scriptCode, countryCode: countryCode);
+	static AppLocale findDeviceLocale() => instance.findDeviceLocale();
+	static List<Locale> get supportedLocales => instance.supportedLocales;
+	static List<String> get supportedLocalesRaw => instance.supportedLocalesRaw;
+}
+
+// translations
+
+// Path: <root>
+class Translations implements BaseTranslations<AppLocale, Translations> {
+	/// Returns the current translations of the given [context].
+	///
+	/// Usage:
+	/// final t = Translations.of(context);
+	static Translations of(BuildContext context) => InheritedLocaleData.of<AppLocale, Translations>(context).translations;
+
+	/// You can call this constructor and build your own translation instance of this locale.
+	/// Constructing via the enum [AppLocale.build] is preferred.
+	Translations.build({Map<String, Node>? overrides, PluralResolver? cardinalResolver, PluralResolver? ordinalResolver})
+		: assert(overrides == null, 'Set "translation_overrides: true" in order to enable this feature.'),
+		  $meta = TranslationMetadata(
+		    locale: AppLocale.ja,
+		    overrides: overrides ?? {},
+		    cardinalResolver: cardinalResolver,
+		    ordinalResolver: ordinalResolver,
+		  ) {
+		$meta.setFlatMapFunction(_flatMapFunction);
+	}
+
+	/// Metadata for the translations of <ja>.
+	@override final TranslationMetadata<AppLocale, Translations> $meta;
+
+	/// Access flat map
+	dynamic operator[](String key) => $meta.getTranslation(key);
+
+	late final Translations _root = this; // ignore: unused_field
+
+	// Translations
+	String get title => 'Flutter App Template';
+	late final _StringsAccountPageJa accountPage = _StringsAccountPageJa._(_root);
+	late final _StringsAppInfoJa appInfo = _StringsAppInfoJa._(_root);
+	late final _StringsAuthorJa author = _StringsAuthorJa._(_root);
+	late final _StringsButtonJa button = _StringsButtonJa._(_root);
+	late final _StringsHomePageJa homePage = _StringsHomePageJa._(_root);
+	late final _StringsNotFoundPageJa notFoundPage = _StringsNotFoundPageJa._(_root);
+	late final _StringsPinkieMewPageJa pinkieMewPage = _StringsPinkieMewPageJa._(_root);
+	late final _StringsSettingsPageJa settingsPage = _StringsSettingsPageJa._(_root);
+	late final _StringsThemeJa theme = _StringsThemeJa._(_root);
+	late final _StringsTopLevelTabJa topLevelTab = _StringsTopLevelTabJa._(_root);
+}
+
+// Path: accountPage
+class _StringsAccountPageJa {
+	_StringsAccountPageJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	late final _StringsAccountPageAppBarJa appBar = _StringsAccountPageAppBarJa._(_root);
+}
+
+// Path: appInfo
+class _StringsAppInfoJa {
+	_StringsAppInfoJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	late final _StringsAppInfoAppBarJa appBar = _StringsAppInfoAppBarJa._(_root);
+}
+
+// Path: author
+class _StringsAuthorJa {
+	_StringsAuthorJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get name => 'Altive株式会社';
+}
+
+// Path: button
+class _StringsButtonJa {
+	_StringsButtonJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get cancel => 'キャンセル';
+	late final _StringsButtonSignJa sign = _StringsButtonSignJa._(_root);
+}
+
+// Path: homePage
+class _StringsHomePageJa {
+	_StringsHomePageJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	late final _StringsHomePageAppBarJa appBar = _StringsHomePageAppBarJa._(_root);
+	late final _StringsHomePageListJa list = _StringsHomePageListJa._(_root);
+}
+
+// Path: notFoundPage
+class _StringsNotFoundPageJa {
+	_StringsNotFoundPageJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get title => '404 Not Found';
+	late final _StringsNotFoundPageHeaderJa header = _StringsNotFoundPageHeaderJa._(_root);
+	String get description => 'is not found.';
+	late final _StringsNotFoundPageBackButtonJa backButton = _StringsNotFoundPageBackButtonJa._(_root);
+}
+
+// Path: pinkieMewPage
+class _StringsPinkieMewPageJa {
+	_StringsPinkieMewPageJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get title => 'Pinkie and Mew';
+}
+
+// Path: settingsPage
+class _StringsSettingsPageJa {
+	_StringsSettingsPageJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	late final _StringsSettingsPageAppBarJa appBar = _StringsSettingsPageAppBarJa._(_root);
+	late final _StringsSettingsPageListJa list = _StringsSettingsPageListJa._(_root);
+}
+
+// Path: theme
+class _StringsThemeJa {
+	_StringsThemeJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	late final _StringsThemeModeJa mode = _StringsThemeModeJa._(_root);
+	late final _StringsThemeSelectionJa selection = _StringsThemeSelectionJa._(_root);
+}
+
+// Path: topLevelTab
+class _StringsTopLevelTabJa {
+	_StringsTopLevelTabJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	late final _StringsTopLevelTabHomeJa home = _StringsTopLevelTabHomeJa._(_root);
+	late final _StringsTopLevelTabRiverpodJa riverpod = _StringsTopLevelTabRiverpodJa._(_root);
+	late final _StringsTopLevelTabSettingsJa settings = _StringsTopLevelTabSettingsJa._(_root);
+}
+
+// Path: accountPage.appBar
+class _StringsAccountPageAppBarJa {
+	_StringsAccountPageAppBarJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get title => 'アカウント';
+}
+
+// Path: appInfo.appBar
+class _StringsAppInfoAppBarJa {
+	_StringsAppInfoAppBarJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get title => 'アプリ情報';
+}
+
+// Path: button.sign
+class _StringsButtonSignJa {
+	_StringsButtonSignJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get out => 'サインアウト';
+}
+
+// Path: homePage.appBar
+class _StringsHomePageAppBarJa {
+	_StringsHomePageAppBarJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get title => 'Home';
+}
+
+// Path: homePage.list
+class _StringsHomePageListJa {
+	_StringsHomePageListJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	late final _StringsHomePageListAppInfoJa appInfo = _StringsHomePageListAppInfoJa._(_root);
+}
+
+// Path: notFoundPage.header
+class _StringsNotFoundPageHeaderJa {
+	_StringsNotFoundPageHeaderJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get label => 'ごめんなさい🙏';
+}
+
+// Path: notFoundPage.backButton
+class _StringsNotFoundPageBackButtonJa {
+	_StringsNotFoundPageBackButtonJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get label => 'is not found.';
+}
+
+// Path: settingsPage.appBar
+class _StringsSettingsPageAppBarJa {
+	_StringsSettingsPageAppBarJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get title => '設定';
+}
+
+// Path: settingsPage.list
+class _StringsSettingsPageListJa {
+	_StringsSettingsPageListJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	late final _StringsSettingsPageListThemeSelectorJa themeSelector = _StringsSettingsPageListThemeSelectorJa._(_root);
+	late final _StringsSettingsPageListAccountJa account = _StringsSettingsPageListAccountJa._(_root);
+}
+
+// Path: theme.mode
+class _StringsThemeModeJa {
+	_StringsThemeModeJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	late final _StringsThemeModeTitleJa title = _StringsThemeModeTitleJa._(_root);
+	late final _StringsThemeModeSubtitleJa subtitle = _StringsThemeModeSubtitleJa._(_root);
+}
+
+// Path: theme.selection
+class _StringsThemeSelectionJa {
+	_StringsThemeSelectionJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	late final _StringsThemeSelectionPageJa page = _StringsThemeSelectionPageJa._(_root);
+}
+
+// Path: topLevelTab.home
+class _StringsTopLevelTabHomeJa {
+	_StringsTopLevelTabHomeJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get label => 'Home';
+}
+
+// Path: topLevelTab.riverpod
+class _StringsTopLevelTabRiverpodJa {
+	_StringsTopLevelTabRiverpodJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	late final _StringsTopLevelTabRiverpodExampleJa example = _StringsTopLevelTabRiverpodExampleJa._(_root);
+}
+
+// Path: topLevelTab.settings
+class _StringsTopLevelTabSettingsJa {
+	_StringsTopLevelTabSettingsJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get label => 'Settings';
+}
+
+// Path: homePage.list.appInfo
+class _StringsHomePageListAppInfoJa {
+	_StringsHomePageListAppInfoJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get label => 'アプリ情報';
+}
+
+// Path: settingsPage.list.themeSelector
+class _StringsSettingsPageListThemeSelectorJa {
+	_StringsSettingsPageListThemeSelectorJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get label => 'テーマ選択';
+}
+
+// Path: settingsPage.list.account
+class _StringsSettingsPageListAccountJa {
+	_StringsSettingsPageListAccountJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get label => 'アカウント';
+}
+
+// Path: theme.mode.title
+class _StringsThemeModeTitleJa {
+	_StringsThemeModeTitleJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get system => 'System';
+	String get light => 'Light theme';
+	String get dark => 'Dark theme';
+}
+
+// Path: theme.mode.subtitle
+class _StringsThemeModeSubtitleJa {
+	_StringsThemeModeSubtitleJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get system => 'システム設定に従う';
+	String get light => '明るいテーマ';
+	String get dark => '暗いテーマ';
+}
+
+// Path: theme.selection.page
+class _StringsThemeSelectionPageJa {
+	_StringsThemeSelectionPageJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	late final _StringsThemeSelectionPageAppBarJa appBar = _StringsThemeSelectionPageAppBarJa._(_root);
+}
+
+// Path: topLevelTab.riverpod.example
+class _StringsTopLevelTabRiverpodExampleJa {
+	_StringsTopLevelTabRiverpodExampleJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get label => 'Riverpod';
+}
+
+// Path: theme.selection.page.appBar
+class _StringsThemeSelectionPageAppBarJa {
+	_StringsThemeSelectionPageAppBarJa._(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+	String get title => 'テーマ選択';
+}
+
+// Path: <root>
+class _StringsEn implements Translations {
+	/// You can call this constructor and build your own translation instance of this locale.
+	/// Constructing via the enum [AppLocale.build] is preferred.
+	_StringsEn.build({Map<String, Node>? overrides, PluralResolver? cardinalResolver, PluralResolver? ordinalResolver})
+		: assert(overrides == null, 'Set "translation_overrides: true" in order to enable this feature.'),
+		  $meta = TranslationMetadata(
+		    locale: AppLocale.en,
+		    overrides: overrides ?? {},
+		    cardinalResolver: cardinalResolver,
+		    ordinalResolver: ordinalResolver,
+		  ) {
+		$meta.setFlatMapFunction(_flatMapFunction);
+	}
+
+	/// Metadata for the translations of <en>.
+	@override final TranslationMetadata<AppLocale, Translations> $meta;
+
+	/// Access flat map
+	@override dynamic operator[](String key) => $meta.getTranslation(key);
+
+	@override late final _StringsEn _root = this; // ignore: unused_field
+
+	// Translations
+	@override String get title => 'Flutter App Template';
+	@override late final _StringsAccountPageEn accountPage = _StringsAccountPageEn._(_root);
+	@override late final _StringsAppInfoEn appInfo = _StringsAppInfoEn._(_root);
+	@override late final _StringsAuthorEn author = _StringsAuthorEn._(_root);
+	@override late final _StringsButtonEn button = _StringsButtonEn._(_root);
+	@override late final _StringsHomePageEn homePage = _StringsHomePageEn._(_root);
+	@override late final _StringsNotFoundPageEn notFoundPage = _StringsNotFoundPageEn._(_root);
+	@override late final _StringsPinkieMewPageEn pinkieMewPage = _StringsPinkieMewPageEn._(_root);
+	@override late final _StringsSettingsPageEn settingsPage = _StringsSettingsPageEn._(_root);
+	@override late final _StringsThemeEn theme = _StringsThemeEn._(_root);
+	@override late final _StringsTopLevelTabEn topLevelTab = _StringsTopLevelTabEn._(_root);
+}
+
+// Path: accountPage
+class _StringsAccountPageEn implements _StringsAccountPageJa {
+	_StringsAccountPageEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override late final _StringsAccountPageAppBarEn appBar = _StringsAccountPageAppBarEn._(_root);
+}
+
+// Path: appInfo
+class _StringsAppInfoEn implements _StringsAppInfoJa {
+	_StringsAppInfoEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override late final _StringsAppInfoAppBarEn appBar = _StringsAppInfoAppBarEn._(_root);
+}
+
+// Path: author
+class _StringsAuthorEn implements _StringsAuthorJa {
+	_StringsAuthorEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get name => 'Altive inc';
+}
+
+// Path: button
+class _StringsButtonEn implements _StringsButtonJa {
+	_StringsButtonEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get cancel => 'Cancel';
+	@override late final _StringsButtonSignEn sign = _StringsButtonSignEn._(_root);
+}
+
+// Path: homePage
+class _StringsHomePageEn implements _StringsHomePageJa {
+	_StringsHomePageEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override late final _StringsHomePageAppBarEn appBar = _StringsHomePageAppBarEn._(_root);
+	@override late final _StringsHomePageListEn list = _StringsHomePageListEn._(_root);
+}
+
+// Path: notFoundPage
+class _StringsNotFoundPageEn implements _StringsNotFoundPageJa {
+	_StringsNotFoundPageEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get title => '404 Not Found';
+	@override late final _StringsNotFoundPageHeaderEn header = _StringsNotFoundPageHeaderEn._(_root);
+	@override String get description => 'is not found.';
+	@override late final _StringsNotFoundPageBackButtonEn backButton = _StringsNotFoundPageBackButtonEn._(_root);
+}
+
+// Path: pinkieMewPage
+class _StringsPinkieMewPageEn implements _StringsPinkieMewPageJa {
+	_StringsPinkieMewPageEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get title => 'Pinkie and Mew';
+}
+
+// Path: settingsPage
+class _StringsSettingsPageEn implements _StringsSettingsPageJa {
+	_StringsSettingsPageEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override late final _StringsSettingsPageAppBarEn appBar = _StringsSettingsPageAppBarEn._(_root);
+	@override late final _StringsSettingsPageListEn list = _StringsSettingsPageListEn._(_root);
+}
+
+// Path: theme
+class _StringsThemeEn implements _StringsThemeJa {
+	_StringsThemeEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override late final _StringsThemeModeEn mode = _StringsThemeModeEn._(_root);
+	@override late final _StringsThemeSelectionEn selection = _StringsThemeSelectionEn._(_root);
+}
+
+// Path: topLevelTab
+class _StringsTopLevelTabEn implements _StringsTopLevelTabJa {
+	_StringsTopLevelTabEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override late final _StringsTopLevelTabHomeEn home = _StringsTopLevelTabHomeEn._(_root);
+	@override late final _StringsTopLevelTabRiverpodEn riverpod = _StringsTopLevelTabRiverpodEn._(_root);
+	@override late final _StringsTopLevelTabSettingsEn settings = _StringsTopLevelTabSettingsEn._(_root);
+}
+
+// Path: accountPage.appBar
+class _StringsAccountPageAppBarEn implements _StringsAccountPageAppBarJa {
+	_StringsAccountPageAppBarEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get title => 'Account';
+}
+
+// Path: appInfo.appBar
+class _StringsAppInfoAppBarEn implements _StringsAppInfoAppBarJa {
+	_StringsAppInfoAppBarEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get title => 'App information';
+}
+
+// Path: button.sign
+class _StringsButtonSignEn implements _StringsButtonSignJa {
+	_StringsButtonSignEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get out => 'Sign out';
+}
+
+// Path: homePage.appBar
+class _StringsHomePageAppBarEn implements _StringsHomePageAppBarJa {
+	_StringsHomePageAppBarEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get title => 'Home';
+}
+
+// Path: homePage.list
+class _StringsHomePageListEn implements _StringsHomePageListJa {
+	_StringsHomePageListEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override late final _StringsHomePageListAppInfoEn appInfo = _StringsHomePageListAppInfoEn._(_root);
+}
+
+// Path: notFoundPage.header
+class _StringsNotFoundPageHeaderEn implements _StringsNotFoundPageHeaderJa {
+	_StringsNotFoundPageHeaderEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get label => 'Sorry...';
+}
+
+// Path: notFoundPage.backButton
+class _StringsNotFoundPageBackButtonEn implements _StringsNotFoundPageBackButtonJa {
+	_StringsNotFoundPageBackButtonEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get label => 'is not found.';
+}
+
+// Path: settingsPage.appBar
+class _StringsSettingsPageAppBarEn implements _StringsSettingsPageAppBarJa {
+	_StringsSettingsPageAppBarEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get title => 'Settings';
+}
+
+// Path: settingsPage.list
+class _StringsSettingsPageListEn implements _StringsSettingsPageListJa {
+	_StringsSettingsPageListEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override late final _StringsSettingsPageListThemeSelectorEn themeSelector = _StringsSettingsPageListThemeSelectorEn._(_root);
+	@override late final _StringsSettingsPageListAccountEn account = _StringsSettingsPageListAccountEn._(_root);
+}
+
+// Path: theme.mode
+class _StringsThemeModeEn implements _StringsThemeModeJa {
+	_StringsThemeModeEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override late final _StringsThemeModeTitleEn title = _StringsThemeModeTitleEn._(_root);
+	@override late final _StringsThemeModeSubtitleEn subtitle = _StringsThemeModeSubtitleEn._(_root);
+}
+
+// Path: theme.selection
+class _StringsThemeSelectionEn implements _StringsThemeSelectionJa {
+	_StringsThemeSelectionEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override late final _StringsThemeSelectionPageEn page = _StringsThemeSelectionPageEn._(_root);
+}
+
+// Path: topLevelTab.home
+class _StringsTopLevelTabHomeEn implements _StringsTopLevelTabHomeJa {
+	_StringsTopLevelTabHomeEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get label => 'Home';
+}
+
+// Path: topLevelTab.riverpod
+class _StringsTopLevelTabRiverpodEn implements _StringsTopLevelTabRiverpodJa {
+	_StringsTopLevelTabRiverpodEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override late final _StringsTopLevelTabRiverpodExampleEn example = _StringsTopLevelTabRiverpodExampleEn._(_root);
+}
+
+// Path: topLevelTab.settings
+class _StringsTopLevelTabSettingsEn implements _StringsTopLevelTabSettingsJa {
+	_StringsTopLevelTabSettingsEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get label => 'Settings';
+}
+
+// Path: homePage.list.appInfo
+class _StringsHomePageListAppInfoEn implements _StringsHomePageListAppInfoJa {
+	_StringsHomePageListAppInfoEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get label => 'App Info';
+}
+
+// Path: settingsPage.list.themeSelector
+class _StringsSettingsPageListThemeSelectorEn implements _StringsSettingsPageListThemeSelectorJa {
+	_StringsSettingsPageListThemeSelectorEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get label => 'Theme Selector';
+}
+
+// Path: settingsPage.list.account
+class _StringsSettingsPageListAccountEn implements _StringsSettingsPageListAccountJa {
+	_StringsSettingsPageListAccountEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get label => 'Account';
+}
+
+// Path: theme.mode.title
+class _StringsThemeModeTitleEn implements _StringsThemeModeTitleJa {
+	_StringsThemeModeTitleEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get system => 'System';
+	@override String get light => 'Light theme';
+	@override String get dark => 'Dark theme';
+}
+
+// Path: theme.mode.subtitle
+class _StringsThemeModeSubtitleEn implements _StringsThemeModeSubtitleJa {
+	_StringsThemeModeSubtitleEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get system => 'Follows the system settings of the device';
+	@override String get light => 'Light';
+	@override String get dark => 'Dark';
+}
+
+// Path: theme.selection.page
+class _StringsThemeSelectionPageEn implements _StringsThemeSelectionPageJa {
+	_StringsThemeSelectionPageEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override late final _StringsThemeSelectionPageAppBarEn appBar = _StringsThemeSelectionPageAppBarEn._(_root);
+}
+
+// Path: topLevelTab.riverpod.example
+class _StringsTopLevelTabRiverpodExampleEn implements _StringsTopLevelTabRiverpodExampleJa {
+	_StringsTopLevelTabRiverpodExampleEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get label => 'Riverpod';
+}
+
+// Path: theme.selection.page.appBar
+class _StringsThemeSelectionPageAppBarEn implements _StringsThemeSelectionPageAppBarJa {
+	_StringsThemeSelectionPageAppBarEn._(this._root);
+
+	@override final _StringsEn _root; // ignore: unused_field
+
+	// Translations
+	@override String get title => 'Theme Selector';
+}
+
+/// Flat map(s) containing all translations.
+/// Only for edge cases! For simple maps, use the map function of this library.
+
+extension on Translations {
+	dynamic _flatMapFunction(String path) {
+		switch (path) {
+			case 'title': return 'Flutter App Template';
+			case 'accountPage.appBar.title': return 'アカウント';
+			case 'appInfo.appBar.title': return 'アプリ情報';
+			case 'author.name': return 'Altive株式会社';
+			case 'button.cancel': return 'キャンセル';
+			case 'button.sign.out': return 'サインアウト';
+			case 'homePage.appBar.title': return 'Home';
+			case 'homePage.list.appInfo.label': return 'アプリ情報';
+			case 'notFoundPage.title': return '404 Not Found';
+			case 'notFoundPage.header.label': return 'ごめんなさい🙏';
+			case 'notFoundPage.description': return 'is not found.';
+			case 'notFoundPage.backButton.label': return 'is not found.';
+			case 'pinkieMewPage.title': return 'Pinkie and Mew';
+			case 'settingsPage.appBar.title': return '設定';
+			case 'settingsPage.list.themeSelector.label': return 'テーマ選択';
+			case 'settingsPage.list.account.label': return 'アカウント';
+			case 'theme.mode.title.system': return 'System';
+			case 'theme.mode.title.light': return 'Light theme';
+			case 'theme.mode.title.dark': return 'Dark theme';
+			case 'theme.mode.subtitle.system': return 'システム設定に従う';
+			case 'theme.mode.subtitle.light': return '明るいテーマ';
+			case 'theme.mode.subtitle.dark': return '暗いテーマ';
+			case 'theme.selection.page.appBar.title': return 'テーマ選択';
+			case 'topLevelTab.home.label': return 'Home';
+			case 'topLevelTab.riverpod.example.label': return 'Riverpod';
+			case 'topLevelTab.settings.label': return 'Settings';
+			default: return null;
+		}
+	}
+}
+
+extension on _StringsEn {
+	dynamic _flatMapFunction(String path) {
+		switch (path) {
+			case 'title': return 'Flutter App Template';
+			case 'accountPage.appBar.title': return 'Account';
+			case 'appInfo.appBar.title': return 'App information';
+			case 'author.name': return 'Altive inc';
+			case 'button.cancel': return 'Cancel';
+			case 'button.sign.out': return 'Sign out';
+			case 'homePage.appBar.title': return 'Home';
+			case 'homePage.list.appInfo.label': return 'App Info';
+			case 'notFoundPage.title': return '404 Not Found';
+			case 'notFoundPage.header.label': return 'Sorry...';
+			case 'notFoundPage.description': return 'is not found.';
+			case 'notFoundPage.backButton.label': return 'is not found.';
+			case 'pinkieMewPage.title': return 'Pinkie and Mew';
+			case 'settingsPage.appBar.title': return 'Settings';
+			case 'settingsPage.list.themeSelector.label': return 'Theme Selector';
+			case 'settingsPage.list.account.label': return 'Account';
+			case 'theme.mode.title.system': return 'System';
+			case 'theme.mode.title.light': return 'Light theme';
+			case 'theme.mode.title.dark': return 'Dark theme';
+			case 'theme.mode.subtitle.system': return 'Follows the system settings of the device';
+			case 'theme.mode.subtitle.light': return 'Light';
+			case 'theme.mode.subtitle.dark': return 'Dark';
+			case 'theme.selection.page.appBar.title': return 'Theme Selector';
+			case 'topLevelTab.home.label': return 'Home';
+			case 'topLevelTab.riverpod.example.label': return 'Riverpod';
+			case 'topLevelTab.settings.label': return 'Settings';
+			default: return null;
+		}
+	}
+}
diff --git a/packages/flutter_app/lib/i18n/app_en.json b/packages/flutter_app/lib/i18n/app_en.json
new file mode 100644
index 00000000..be007029
--- /dev/null
+++ b/packages/flutter_app/lib/i18n/app_en.json
@@ -0,0 +1,93 @@
+{
+  "@@locale": "en",
+  "title": "Flutter App Template",
+  "accountPage": {
+    "appBar": {
+      "title": "Account"
+    }
+  },
+  "appInfo": {
+    "appBar": {
+      "title": "App information"
+    }
+  },
+  "author": {
+    "name": "Altive inc"
+  },
+  "button": {
+    "cancel": "Cancel",
+    "sign": {
+      "out": "Sign out"
+    }
+  },
+  "homePage": {
+    "appBar": {
+      "title": "Home"
+    },
+    "list": {
+      "appInfo": {
+        "label": "App Info"
+      }
+    }
+  },
+  "notFoundPage": {
+    "title": "404 Not Found",
+    "header": {
+      "label": "Sorry..."
+    },
+    "description": "is not found.",
+    "backButton": {
+      "label": "is not found."
+    }
+  },
+  "pinkieMewPage": {
+    "title": "Pinkie and Mew"
+  },
+  "settingsPage": {
+    "appBar": {
+      "title": "Settings"
+    },
+    "list": {
+      "themeSelector": {
+        "label": "Theme Selector"
+      },
+      "account": {
+        "label": "Account"
+      }
+    }
+  },
+  "theme": {
+    "mode": {
+      "title": {
+        "system": "System",
+        "light": "Light theme",
+        "dark": "Dark theme"
+      },
+      "subtitle": {
+        "system": "Follows the system settings of the device",
+        "light": "Light",
+        "dark": "Dark"
+      }
+    },
+    "selection": {
+      "page": {
+        "appBar": {
+          "title": "Theme Selector"
+        }
+      }
+    }
+  },
+  "topLevelTab": {
+    "home": {
+      "label": "Home"
+    },
+    "riverpod": {
+      "example": {
+        "label": "Riverpod"
+      }
+    },
+    "settings": {
+      "label": "Settings"
+    }
+  }
+}
\ No newline at end of file
diff --git a/packages/flutter_app/lib/i18n/app_ja.json b/packages/flutter_app/lib/i18n/app_ja.json
new file mode 100644
index 00000000..1c769726
--- /dev/null
+++ b/packages/flutter_app/lib/i18n/app_ja.json
@@ -0,0 +1,93 @@
+{
+  "@@locale": "ja",
+  "title": "Flutter App Template",
+  "accountPage": {
+    "appBar": {
+      "title": "アカウント"
+    }
+  },
+  "appInfo": {
+    "appBar": {
+      "title": "アプリ情報"
+    }
+  },
+  "author": {
+    "name": "Altive株式会社"
+  },
+  "button": {
+    "cancel": "キャンセル",
+    "sign": {
+      "out": "サインアウト"
+    }
+  },
+  "homePage": {
+    "appBar": {
+      "title": "Home"
+    },
+    "list": {
+      "appInfo": {
+        "label": "アプリ情報"
+      }
+    }
+  },
+  "notFoundPage": {
+    "title": "404 Not Found",
+    "header": {
+      "label": "ごめんなさい🙏"
+    },
+    "description": "is not found.",
+    "backButton": {
+      "label": "is not found."
+    }
+  },
+  "pinkieMewPage": {
+    "title": "Pinkie and Mew"
+  },
+  "settingsPage": {
+    "appBar": {
+      "title": "設定"
+    },
+    "list": {
+      "themeSelector": {
+        "label": "テーマ選択"
+      },
+      "account": {
+        "label": "アカウント"
+      }
+    }
+  },
+  "theme": {
+    "mode": {
+      "title": {
+        "system": "System",
+        "light": "Light theme",
+        "dark": "Dark theme"
+      },
+      "subtitle": {
+        "system": "システム設定に従う",
+        "light": "明るいテーマ",
+        "dark": "暗いテーマ"
+      }
+    },
+    "selection": {
+      "page": {
+        "appBar": {
+          "title": "テーマ選択"
+        }
+      }
+    }
+  },
+  "topLevelTab": {
+    "home": {
+      "label": "Home"
+    },
+    "riverpod": {
+      "example": {
+        "label": "Riverpod"
+      }
+    },
+    "settings": {
+      "label": "Settings"
+    }
+  }
+}
\ No newline at end of file
diff --git a/packages/flutter_app/lib/l10n/app_en.arb b/packages/flutter_app/lib/l10n/app_en.arb
deleted file mode 100644
index e78c5655..00000000
--- a/packages/flutter_app/lib/l10n/app_en.arb
+++ /dev/null
@@ -1,57 +0,0 @@
-{
-    "@@locale": "en",
-    "title": "Flutter App Template",
-    "accountPageAppBarTitle": "Account",
-    "appInfoAppBarTitle": "App information",
-    "authorName": "Altive inc",
-    "buttonAdd": "Add",
-    "buttonCancel": "Cancel",
-    "buttonDelete": "Delete",
-    "buttonDone": "Done",
-    "buttonOK": "OK",
-    "buttonSignOut": "Sign out",
-    "buttonUnlink": "Unlink",
-    "buttonUpdate": "Update",
-    "buttonRemovePhoto": "Remove photo",
-    "buttonTakeNewPhoto": "Take new photo",
-    "buttonSelectNewPhoto": "Select new Photo",
-    "homePageAppBarTitle": "Home",
-    "homePageListAppInfoLabel": "App Info",
-    "homePageListRiverpodExampleLabel": "Riverpod Examples",
-    "homePageListTo404Label": "To 404",
-    "notFoundPageTitle": "404 Not Found",
-    "notFoundPageHeaderLabel": "Sorry...",
-    "notFoundPageDescription": "is not found.",
-    "notFoundPageReturnButtonLabel": "is not found.",
-    "pinkieMewPageTitle": "Pinkie and Mew",
-    "settingsPageAppBarTitle": "Settings",
-    "settingsPageListThemeSelectorLabel": "Theme Selector",
-    "settingsPageListAccountLabel": "Account",
-    "signInMethodAnonymous": "Anonymous",
-    "signInMethodApple": "Apple",
-    "signInMethodGoogle": "Google",
-    "signInPageAnonymousButton": "Continue with Guest",
-    "signInPageAppleButton": "Continue with Apple",
-    "signInPageGoogleButton": "Continue with Google",
-    "themeModeTitleSystem": "System",
-    "themeModeTitleLight": "Light theme",
-    "themeModeTitleDark": "Dark theme",
-    "themeModeSubtitleSystem": "Follows the system settings of the device",
-    "themeModeSubtitleLight": "Light",
-    "themeModeSubtitleDark": "Dark",
-    "themeSelectionPageAppBarTitle": "Theme Selector",
-    "titleChangePhoto": "Change photo",
-    "topLevelTabHomeLabel": "Home",
-    "topLevelTabRiverpodExampleLabel": "Riverpod",
-    "topLevelTabSettingsLabel": "Settings",
-    "hello": "Hello {userName}!",
-    "@hello": {
-        "description": "A message with a single parameter.",
-        "placeholders": {
-            "userName": {
-                "type": "String",
-                "example": "Bob"
-            }
-        }
-    }
-}
\ No newline at end of file
diff --git a/packages/flutter_app/lib/l10n/app_ja.arb b/packages/flutter_app/lib/l10n/app_ja.arb
deleted file mode 100644
index d9c22bc0..00000000
--- a/packages/flutter_app/lib/l10n/app_ja.arb
+++ /dev/null
@@ -1,48 +0,0 @@
-{
-    "@@locale": "ja",
-    "title": "Flutter App Template",
-    "accountPageAppBarTitle": "アカウント",
-    "appInfoAppBarTitle": "アプリ情報",
-    "authorName": "Altive株式会社",
-    "buttonAdd": "追加",
-    "buttonCancel": "キャンセル",
-    "buttonDelete": "削除",
-    "buttonDone": "完了",
-    "buttonOK": "OK",
-    "buttonSignOut": "サインアウト",
-    "buttonUnlink": "連携解除",
-    "buttonUpdate": "更新",
-    "buttonRemovePhoto": "写真を削除",
-    "buttonTakeNewPhoto": "カメラで撮影",
-    "buttonSelectNewPhoto": "写真を選ぶ",
-    "homePageAppBarTitle": "Home",
-    "homePageListAppInfoLabel": "アプリ情報",
-    "homePageListRiverpodExampleLabel": "Riverpod Examples",
-    "homePageListTo404Label": "To 404",
-    "notFoundPageTitle": "404 Not Found",
-    "notFoundPageHeaderLabel": "ごめんなさい🙏",
-    "notFoundPageDescription": "is not found.",
-    "notFoundPageReturnButtonLabel": "is not found.",
-    "pinkieMewPageTitle": "Pinkie and Mew",
-    "settingsPageAppBarTitle": "設定",
-    "settingsPageListThemeSelectorLabel": "テーマ選択",
-    "settingsPageListAccountLabel": "アカウント",
-    "signInMethodAnonymous": "匿名",
-    "signInMethodApple": "Apple",
-    "signInMethodGoogle": "Google",
-    "signInPageAnonymousButton": "ゲストではじめる",
-    "signInPageAppleButton": "Appleではじめる",
-    "signInPageGoogleButton": "Googleではじめる",
-    "themeModeTitleSystem": "System",
-    "themeModeTitleLight": "Light theme",
-    "themeModeTitleDark": "Dark theme",
-    "themeModeSubtitleSystem": "システム設定に従う",
-    "themeModeSubtitleLight": "明るいテーマ",
-    "themeModeSubtitleDark": "暗いテーマ",
-    "themeSelectionPageAppBarTitle": "テーマ選択",
-    "titleChangePhoto": "写真を変更",
-    "topLevelTabHomeLabel": "Home",
-    "topLevelTabRiverpodExampleLabel": "Riverpod",
-    "topLevelTabSettingsLabel": "Setting",
-    "hello": "こんにちは、{userName}！"
-}
\ No newline at end of file
diff --git a/packages/flutter_app/lib/main.dart b/packages/flutter_app/lib/main.dart
index 86e964b1..a314b4cf 100644
--- a/packages/flutter_app/lib/main.dart
+++ b/packages/flutter_app/lib/main.dart
@@ -11,6 +11,7 @@ import 'package:shared_preferences/shared_preferences.dart';
 import 'environment/environment.dart';
 import 'features/user_device/user_device.dart';
 import 'flutter_app.dart';
+import 'gen/strings.g.dart';
 import 'package_adaptor/analysis_logger/analysis_logger_provider.dart';
 import 'util/logger/provider_logger.dart';
 import 'util/providers/providers.dart';
@@ -45,7 +46,9 @@ Future<void> main() async {
         analysisLoggerProvider.overrideWithValue(analysisLogger),
       ],
       observers: [ProviderLogger()],
-      child: const FlutterApp(),
+      child: TranslationProvider(
+        child: const FlutterApp(),
+      ),
     ),
   );
 }
diff --git a/packages/flutter_app/lib/pages/account/components/account_page_app_bar.dart b/packages/flutter_app/lib/pages/account/components/account_page_app_bar.dart
index 66676ce1..257310e6 100644
--- a/packages/flutter_app/lib/pages/account/components/account_page_app_bar.dart
+++ b/packages/flutter_app/lib/pages/account/components/account_page_app_bar.dart
@@ -1,7 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:themes/themes.dart';
 
-import '../../../util/localizer/localizer.dart';
+import '../../../gen/strings.g.dart';
 
 class AccountPageAppBar extends StatelessWidget implements PreferredSizeWidget {
   const AccountPageAppBar({super.key});
@@ -11,9 +11,9 @@ class AccountPageAppBar extends StatelessWidget implements PreferredSizeWidget {
 
   @override
   Widget build(BuildContext context) {
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     return AppBar(
-      title: Text(l10n.accountPageAppBarTitle),
+      title: Text(t.accountPage.appBar.title),
     );
   }
 }
diff --git a/packages/flutter_app/lib/pages/account/components/account_page_body.dart b/packages/flutter_app/lib/pages/account/components/account_page_body.dart
index 84b5248b..ba186d7e 100644
--- a/packages/flutter_app/lib/pages/account/components/account_page_body.dart
+++ b/packages/flutter_app/lib/pages/account/components/account_page_body.dart
@@ -3,14 +3,14 @@ import 'package:awaitable_button/awaitable_button.dart';
 import 'package:flutter/material.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 
-import '../../../util/localizer/localizer.dart';
+import '../../../gen/strings.g.dart';
 
 class AccountPageBody extends HookConsumerWidget {
   const AccountPageBody({super.key});
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     final authenticator = ref.watch(authenticatorProvider);
     Future<void> signOut() async {
       final isBool = await showDialog<bool>(
@@ -22,11 +22,11 @@ class AccountPageBody extends HookConsumerWidget {
             actions: [
               TextButton(
                 onPressed: () => Navigator.pop(context, false),
-                child: Text(l10n.buttonCancel),
+                child: Text(t.button.cancel),
               ),
               TextButton(
                 onPressed: () => Navigator.pop(context, true),
-                child: Text(l10n.buttonSignOut),
+                child: Text(t.button.sign.out),
               ),
             ],
           );
@@ -47,7 +47,7 @@ class AccountPageBody extends HookConsumerWidget {
         ),
         AwaitableTextButton<void>(
           onPressed: signOut,
-          child: Text(l10n.buttonSignOut),
+          child: Text(t.button.sign.out),
         ),
       ],
     );
diff --git a/packages/flutter_app/lib/pages/app_info_page/components/app_info_app_bar.dart b/packages/flutter_app/lib/pages/app_info_page/components/app_info_app_bar.dart
index cf9b96ba..6d88895c 100644
--- a/packages/flutter_app/lib/pages/app_info_page/components/app_info_app_bar.dart
+++ b/packages/flutter_app/lib/pages/app_info_page/components/app_info_app_bar.dart
@@ -1,7 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:themes/themes.dart';
 
-import '../../../util/localizer/localizer.dart';
+import '../../../gen/strings.g.dart';
 
 class AppInfoAppBar extends StatelessWidget implements PreferredSizeWidget {
   const AppInfoAppBar({super.key});
@@ -11,9 +11,9 @@ class AppInfoAppBar extends StatelessWidget implements PreferredSizeWidget {
 
   @override
   Widget build(BuildContext context) {
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     return AppBar(
-      title: Text(l10n.appInfoAppBarTitle),
+      title: Text(t.appInfo.appBar.title),
     );
   }
 }
diff --git a/packages/flutter_app/lib/pages/app_info_page/components/app_info_body.dart b/packages/flutter_app/lib/pages/app_info_page/components/app_info_body.dart
index 6d37ccff..2c7904d8 100644
--- a/packages/flutter_app/lib/pages/app_info_page/components/app_info_body.dart
+++ b/packages/flutter_app/lib/pages/app_info_page/components/app_info_body.dart
@@ -3,7 +3,7 @@ import 'package:gap/gap.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 
 import '../../../environment/environment.dart';
-import '../../../util/localizer/localizer.dart';
+import '../../../gen/strings.g.dart';
 import '../../../util/providers/package_info_provider.dart';
 import '../../../widgets/widgets.dart';
 
@@ -12,14 +12,14 @@ class AppInfoBody extends HookConsumerWidget {
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     final flavor = ref.watch(flavorProvider);
     final packageInfo = ref.watch(packageInfoProvider);
     return ListView(
       children: <Widget>[
-        Text(l10n.title),
+        Text(t.title),
         const Gap(8),
-        Text('Author is ${l10n.authorName}.'),
+        Text('Author is ${t.author.name}.'),
         const Gap(8),
         const Text('Developed by Ryunosuke Muramatsu.'),
         const Divider(),
diff --git a/packages/flutter_app/lib/pages/home_page/components/home_page_app_bar.dart b/packages/flutter_app/lib/pages/home_page/components/home_page_app_bar.dart
index cfae3d21..0cd2f56e 100644
--- a/packages/flutter_app/lib/pages/home_page/components/home_page_app_bar.dart
+++ b/packages/flutter_app/lib/pages/home_page/components/home_page_app_bar.dart
@@ -1,7 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:themes/themes.dart';
 
-import '../../../util/localizer/localizer.dart';
+import '../../../gen/strings.g.dart';
 
 class HomePageAppBar extends StatelessWidget implements PreferredSizeWidget {
   const HomePageAppBar({super.key});
@@ -11,9 +11,9 @@ class HomePageAppBar extends StatelessWidget implements PreferredSizeWidget {
 
   @override
   Widget build(BuildContext context) {
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     return AppBar(
-      title: Text(l10n.homePageAppBarTitle),
+      title: Text(t.homePage.appBar.title),
     );
   }
 }
diff --git a/packages/flutter_app/lib/pages/home_page/components/home_page_body.dart b/packages/flutter_app/lib/pages/home_page/components/home_page_body.dart
index 54fd9c25..122475c2 100644
--- a/packages/flutter_app/lib/pages/home_page/components/home_page_body.dart
+++ b/packages/flutter_app/lib/pages/home_page/components/home_page_body.dart
@@ -1,8 +1,8 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 
+import '../../../gen/strings.g.dart';
 import '../../../router/router.dart';
-import '../../../util/localizer/localizer.dart';
 import 'home_list_card.dart';
 
 class HomePageBody extends HookWidget {
@@ -12,13 +12,13 @@ class HomePageBody extends HookWidget {
 
   @override
   Widget build(BuildContext context) {
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     return ListView(
       padding: const EdgeInsets.all(16),
       children: [
         HomeListCard(
           onTap: () => const AppInfoRouteData().go(context),
-          label: l10n.homePageListAppInfoLabel,
+          label: t.homePage.list.appInfo.label,
         ),
         HomeListCard(
           onTap: () => const RiverpodExampleRouteData().go(context),
diff --git a/packages/flutter_app/lib/pages/not_found_page/components/not_found_app_bar.dart b/packages/flutter_app/lib/pages/not_found_page/components/not_found_app_bar.dart
index 01bf9ff4..8b5b60a5 100644
--- a/packages/flutter_app/lib/pages/not_found_page/components/not_found_app_bar.dart
+++ b/packages/flutter_app/lib/pages/not_found_page/components/not_found_app_bar.dart
@@ -1,7 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:themes/themes.dart';
 
-import '../../../util/localizer/localizer.dart';
+import '../../../gen/strings.g.dart';
 
 class NotFoundAppBar extends StatelessWidget implements PreferredSizeWidget {
   const NotFoundAppBar({super.key});
@@ -11,9 +11,9 @@ class NotFoundAppBar extends StatelessWidget implements PreferredSizeWidget {
 
   @override
   Widget build(BuildContext context) {
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     return AppBar(
-      title: Text(l10n.notFoundPageTitle),
+      title: Text(t.notFoundPage.title),
     );
   }
 }
diff --git a/packages/flutter_app/lib/pages/not_found_page/components/not_found_page_body.dart b/packages/flutter_app/lib/pages/not_found_page/components/not_found_page_body.dart
index d7ca3dce..a990ae48 100644
--- a/packages/flutter_app/lib/pages/not_found_page/components/not_found_page_body.dart
+++ b/packages/flutter_app/lib/pages/not_found_page/components/not_found_page_body.dart
@@ -2,8 +2,8 @@ import 'package:flutter/material.dart';
 import 'package:gap/gap.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 
+import '../../../gen/strings.g.dart';
 import '../../../router/router.dart';
-import '../../../util/localizer/localizer.dart';
 import '../../../widgets/widgets.dart';
 
 class NotFoundPageBody extends HookConsumerWidget {
@@ -16,19 +16,19 @@ class NotFoundPageBody extends HookConsumerWidget {
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
-        Text(l10n.notFoundPageHeaderLabel),
+        Text(t.notFoundPage.header.label),
         const Gap(32),
         DisplaySmallText(path),
         const Gap(32),
-        Text(l10n.notFoundPageDescription),
+        Text(t.notFoundPage.description),
         Center(
           child: ElevatedButton(
             onPressed: () => const HomeRouteData().go(context),
-            child: Text(l10n.notFoundPageReturnButtonLabel),
+            child: Text(t.notFoundPage.backButton.label),
           ),
         ),
       ],
diff --git a/packages/flutter_app/lib/pages/pinkie_mew/components/pinkie_mew_page_app_bar.dart b/packages/flutter_app/lib/pages/pinkie_mew/components/pinkie_mew_page_app_bar.dart
index da52aaf5..f64983cf 100644
--- a/packages/flutter_app/lib/pages/pinkie_mew/components/pinkie_mew_page_app_bar.dart
+++ b/packages/flutter_app/lib/pages/pinkie_mew/components/pinkie_mew_page_app_bar.dart
@@ -1,7 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:themes/themes.dart';
 
-import '../../../util/localizer/localizer.dart';
+import '../../../gen/strings.g.dart';
 
 class PinkieMewPageAppBar extends StatelessWidget
     implements PreferredSizeWidget {
@@ -12,9 +12,9 @@ class PinkieMewPageAppBar extends StatelessWidget
 
   @override
   Widget build(BuildContext context) {
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     return AppBar(
-      title: Text(l10n.pinkieMewPageTitle),
+      title: Text(t.pinkieMewPage.title),
     );
   }
 }
diff --git a/packages/flutter_app/lib/pages/settings_page/components/settings_page_app_bar.dart b/packages/flutter_app/lib/pages/settings_page/components/settings_page_app_bar.dart
index 33536057..dab50082 100644
--- a/packages/flutter_app/lib/pages/settings_page/components/settings_page_app_bar.dart
+++ b/packages/flutter_app/lib/pages/settings_page/components/settings_page_app_bar.dart
@@ -1,7 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:themes/themes.dart';
 
-import '../../../util/localizer/localizer.dart';
+import '../../../gen/strings.g.dart';
 
 class SettingsPageAppBar extends StatelessWidget
     implements PreferredSizeWidget {
@@ -12,9 +12,9 @@ class SettingsPageAppBar extends StatelessWidget
 
   @override
   Widget build(BuildContext context) {
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     return AppBar(
-      title: Text(l10n.settingsPageAppBarTitle),
+      title: Text(t.settingsPage.appBar.title),
     );
   }
 }
diff --git a/packages/flutter_app/lib/pages/settings_page/components/settings_page_body.dart b/packages/flutter_app/lib/pages/settings_page/components/settings_page_body.dart
index f399eb8c..98b4b75c 100644
--- a/packages/flutter_app/lib/pages/settings_page/components/settings_page_body.dart
+++ b/packages/flutter_app/lib/pages/settings_page/components/settings_page_body.dart
@@ -2,15 +2,15 @@ import 'package:flutter/material.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 
 import '../../../features/user_device/user_device.dart';
+import '../../../gen/strings.g.dart';
 import '../../../router/router.dart';
-import '../../../util/localizer/localizer.dart';
 
 class SettingsPageBody extends HookConsumerWidget {
   const SettingsPageBody({super.key});
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     final userDevice = ref.watch(userDeviceProvider);
     return ListView(
       padding: const EdgeInsets.all(16),
@@ -18,13 +18,13 @@ class SettingsPageBody extends HookConsumerWidget {
         Card(
           child: ListTile(
             onTap: () => const ThemeSelectionRouteData().go(context),
-            title: Text(l10n.settingsPageListThemeSelectorLabel),
+            title: Text(t.settingsPage.list.themeSelector.label),
           ),
         ),
         Card(
           child: ListTile(
             onTap: () => const AccountRouteData().go(context),
-            title: Text(l10n.settingsPageListAccountLabel),
+            title: Text(t.settingsPage.list.account.label),
           ),
         ),
         ListTile(
diff --git a/packages/flutter_app/lib/pages/theme_selection_page/components/theme_selection_page_app_bar.dart b/packages/flutter_app/lib/pages/theme_selection_page/components/theme_selection_page_app_bar.dart
index 50fa9377..d7aca49a 100644
--- a/packages/flutter_app/lib/pages/theme_selection_page/components/theme_selection_page_app_bar.dart
+++ b/packages/flutter_app/lib/pages/theme_selection_page/components/theme_selection_page_app_bar.dart
@@ -2,7 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:gap/gap.dart';
 import 'package:themes/themes.dart';
 
-import '../../../util/localizer/localizer.dart';
+import '../../../gen/strings.g.dart';
 import '../../../widgets/widgets.dart';
 
 class ThemeSelectionPageAppBar extends StatelessWidget
@@ -14,10 +14,10 @@ class ThemeSelectionPageAppBar extends StatelessWidget
 
   @override
   Widget build(BuildContext context) {
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     final themeDescription = context.themeDescription;
     return AppBar(
-      title: Text(l10n.themeSelectionPageAppBarTitle),
+      title: Text(t.theme.selection.page.appBar.title),
       actions: [
         themeDescription.icon,
         Align(
diff --git a/packages/flutter_app/lib/pages/theme_selection_page/components/theme_selection_page_body.dart b/packages/flutter_app/lib/pages/theme_selection_page/components/theme_selection_page_body.dart
index 1d91b454..384ed60f 100644
--- a/packages/flutter_app/lib/pages/theme_selection_page/components/theme_selection_page_body.dart
+++ b/packages/flutter_app/lib/pages/theme_selection_page/components/theme_selection_page_body.dart
@@ -2,7 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 
 import '../../../features/theme_selector/theme_selector.dart';
-import '../../../util/localizer/localizer.dart';
+import '../../../gen/strings.g.dart';
 
 class ThemeSelectionPageBody extends HookConsumerWidget {
   const ThemeSelectionPageBody({super.key});
@@ -11,7 +11,7 @@ class ThemeSelectionPageBody extends HookConsumerWidget {
   Widget build(BuildContext context, WidgetRef ref) {
     final themeSelector = ref.watch(themeSelectorProvider.notifier);
     final currentThemeMode = ref.watch(themeSelectorProvider);
-    final l10n = L10n.of(context);
+    final t = Translations.of(context);
     return ListView.builder(
       padding: const EdgeInsets.symmetric(vertical: 16),
       itemCount: ThemeMode.values.length,
@@ -21,8 +21,8 @@ class ThemeSelectionPageBody extends HookConsumerWidget {
           value: themeMode,
           groupValue: currentThemeMode,
           onChanged: (newTheme) async => themeSelector.changeAndSave(newTheme!),
-          title: Text(themeMode.title(l10n)),
-          subtitle: Text(themeMode.subtitle(l10n)),
+          title: Text(themeMode.title(t)),
+          subtitle: Text(themeMode.subtitle(t)),
           secondary: Icon(themeMode.iconData),
         );
       },
diff --git a/packages/flutter_app/lib/pages/top_level_tab/top_level_tab.dart b/packages/flutter_app/lib/pages/top_level_tab/top_level_tab.dart
index 3fc6f66c..00fe6ca4 100644
--- a/packages/flutter_app/lib/pages/top_level_tab/top_level_tab.dart
+++ b/packages/flutter_app/lib/pages/top_level_tab/top_level_tab.dart
@@ -1,6 +1,6 @@
 import 'package:flutter/material.dart';
-import 'package:flutter_gen/gen_l10n/app_localizations.dart';
 
+import '../../gen/strings.g.dart';
 import '../home_page/home_page.dart';
 import '../riverpod_example_page/riverpod_example_page.dart';
 import '../settings_page/settings_page.dart';
@@ -30,14 +30,14 @@ enum TopLevelTab {
 }
 
 extension TopLevelTabExt on TopLevelTab {
-  String labelText(AppLocalizations l10n) {
+  String labelText(Translations t) {
     switch (this) {
       case TopLevelTab.home:
-        return l10n.topLevelTabHomeLabel;
+        return t.topLevelTab.home.label;
       case TopLevelTab.riverpod:
-        return l10n.topLevelTabRiverpodExampleLabel;
+        return t.topLevelTab.riverpod.example.label;
       case TopLevelTab.settings:
-        return l10n.topLevelTabSettingsLabel;
+        return t.topLevelTab.settings.label;
     }
   }
 }
diff --git a/packages/flutter_app/lib/util/localizer/localizer.dart b/packages/flutter_app/lib/util/localizer/localizer.dart
deleted file mode 100644
index 552767e5..00000000
--- a/packages/flutter_app/lib/util/localizer/localizer.dart
+++ /dev/null
@@ -1,18 +0,0 @@
-import 'package:flutter/widgets.dart';
-import 'package:flutter_gen/gen_l10n/app_localizations.dart';
-
-extension L10n on AppLocalizations {
-  /// `L10n.of(context)`
-  ///
-  /// `AppLocalizations.of(context)` の以下2つの問題を解決するための実装
-  /// 1. IDEでサジェストされない（自動でインポートされない）
-  /// 2. 取得できるAppLocalizationsがNullable
-  /// この代替メソッドでは両問題を解決している
-  static AppLocalizations of(BuildContext context) =>
-      AppLocalizations.of(context)!;
-}
-
-extension BuildContextL10n on BuildContext {
-  /// `context.l10n`
-  AppLocalizations get l10n => L10n.of(this);
-}
diff --git a/packages/flutter_app/pubspec.lock b/packages/flutter_app/pubspec.lock
index 64f1c52a..948f9a12 100644
--- a/packages/flutter_app/pubspec.lock
+++ b/packages/flutter_app/pubspec.lock
@@ -302,6 +302,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.0.3"
+  csv:
+    dependency: transitive
+    description:
+      name: csv
+      sha256: "63ed2871dd6471193dffc52c0e6c76fb86269c00244d244297abbb355c84a86e"
+      url: "https://pub.dev"
+    source: hosted
+    version: "5.1.1"
   cupertino_icons:
     dependency: "direct main"
     description:
@@ -930,6 +938,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.6.7"
+  json2yaml:
+    dependency: transitive
+    description:
+      name: json2yaml
+      sha256: da94630fbc56079426fdd167ae58373286f603371075b69bf46d848d63ba3e51
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.0.1"
   json_annotation:
     dependency: "direct main"
     description:
@@ -1318,6 +1334,30 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.99"
+  slang:
+    dependency: "direct main"
+    description:
+      name: slang
+      sha256: "3231d9b11163acb96e7611c5da54404e93d1e0d0eb8f31126ce86a1a43a1c7d4"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.26.2"
+  slang_build_runner:
+    dependency: "direct dev"
+    description:
+      name: slang_build_runner
+      sha256: "3c1efe9cc32af091859962fc67d68aedf8e649ac758348f3b2ecf4942b2eac4a"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.26.2"
+  slang_flutter:
+    dependency: "direct main"
+    description:
+      name: slang_flutter
+      sha256: "88e40b238307abdc191c9c26cdfb7c1b6d5075f461e8fbcf89f6f2a3f92cd5d7"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.26.2"
   sort_key_generator:
     dependency: "direct main"
     description:
diff --git a/packages/flutter_app/pubspec.yaml b/packages/flutter_app/pubspec.yaml
index 0d56c0a5..ed44e5f1 100644
--- a/packages/flutter_app/pubspec.yaml
+++ b/packages/flutter_app/pubspec.yaml
@@ -47,6 +47,8 @@ dependencies:
   riverpod_annotation: ^2.1.5
   shared_preferences: ^2.2.2
   simple_logger: ^1.9.0+1
+  slang: ^3.26.2
+  slang_flutter: ^3.26.2
   sort_key_generator: ^0.2.0+1
   themes:
     path: ../themes/
@@ -69,6 +71,7 @@ dev_dependencies:
   mockito: ^5.2.0
   riverpod_generator: ^2.3.2
   riverpod_lint: ^2.1.0
+  slang_build_runner: ^3.26.2
 
 flutter_gen:
   enabled: true
diff --git a/packages/flutter_app/slang.yaml b/packages/flutter_app/slang.yaml
new file mode 100644
index 00000000..c5ac732c
--- /dev/null
+++ b/packages/flutter_app/slang.yaml
@@ -0,0 +1,4 @@
+base_locale: ja
+input_directory: lib/i18n
+input_file_pattern: .json
+output_directory: lib/gen
diff --git a/packages/util/analysis_options.yaml b/packages/util/analysis_options.yaml
index ff442717..1ef0ad32 100644
--- a/packages/util/analysis_options.yaml
+++ b/packages/util/analysis_options.yaml
@@ -1,6 +1,5 @@
 include: package:altive_lints/altive_lints.yaml
 analyzer:
   exclude:
-    - "**/l10n/*.dart"
     - "**/gen/*.dart"
     - "lib/environment/src/firebase_options*.dart"