diff --git a/.github/workflows/add-release-assets.yml b/.github/workflows/add-release-assets.yml
index 828c62de..f5b86f1d 100644
--- a/.github/workflows/add-release-assets.yml
+++ b/.github/workflows/add-release-assets.yml
@@ -10,9 +10,9 @@ env:
 
 jobs:
   build:
-    runs-on: macos-13
+    runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Generate API reference doc
       run: |
         swift package --allow-writing-to-directory $DOC_ARCH \
diff --git a/.github/workflows/gh-pages.yml b/.github/workflows/gh-pages.yml
index 600cba13..68fae3dd 100644
--- a/.github/workflows/gh-pages.yml
+++ b/.github/workflows/gh-pages.yml
@@ -11,9 +11,9 @@ env:
 
 jobs:
   build:
-    runs-on: macos-13
+    runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Generate API reference doc
       run: |
         swift package --allow-writing-to-directory $OUTPUT_PATH \
diff --git a/.github/workflows/swift-integration.yml b/.github/workflows/swift-integration.yml
index cd099ff4..4fadfa28 100644
--- a/.github/workflows/swift-integration.yml
+++ b/.github/workflows/swift-integration.yml
@@ -20,5 +20,3 @@ jobs:
     - run: docker-compose -f docker/docker-compose-ci.yml up --build -d
     - name: Run tests
       run: swift test --enable-code-coverage -v --filter YorkieIntegrationTests
-    
-
diff --git a/.github/workflows/swift.yml b/.github/workflows/swift.yml
index 8550fadb..fa3f3f4d 100644
--- a/.github/workflows/swift.yml
+++ b/.github/workflows/swift.yml
@@ -8,12 +8,14 @@ on:
 
 jobs:
   build:
-    runs-on: macos-13
+    runs-on: macos-14
     steps:
     - uses: maxim-lobanov/setup-xcode@v1
       with:
-        xcode-version: latest-stable
-    - uses: actions/checkout@v3
+        xcode-version: '15.3'
+    - uses: actions/checkout@v4
+    - name: SwiftLint install
+      run: brew install swiftlint
     - name: SwiftLint
       run: swiftlint lint --strict
     - name: SwiftFormat
@@ -23,7 +25,7 @@ jobs:
     - name: Prepare Code Coverage
       run: xcrun llvm-cov export -format="lcov" .build/debug/YorkiePackageTests.xctest/Contents/MacOS/YorkiePackageTests -instr-profile .build/debug/codecov/default.profdata > lcov.info
     - name: Upload coverage to Codecov
-      uses: codecov/codecov-action@v3
+      uses: codecov/codecov-action@v4
       with:
         file: lcov.info
       env:
diff --git a/Sources/API/Converter.swift b/Sources/API/Converter.swift
index c3fa1e5f..71b2414f 100644
--- a/Sources/API/Converter.swift
+++ b/Sources/API/Converter.swift
@@ -431,6 +431,7 @@ extension Converter {
             treeStyleOperation.attributes.forEach { key, value in
                 pbTreeStyleOperation.attributes[key] = value
             }
+            pbTreeStyleOperation.attributesToRemove = treeStyleOperation.attributesToRemove
             pbTreeStyleOperation.executedAt = toTimeTicket(treeStyleOperation.executedAt)
             pbOperation.treeStyle = pbTreeStyleOperation
         } else {
@@ -510,7 +511,8 @@ extension Converter {
                 return TreeStyleOperation(parentCreatedAt: fromTimeTicket(pbTreeStyleOperation.parentCreatedAt),
                                           fromPos: fromTreePos(pbTreeStyleOperation.from),
                                           toPos: fromTreePos(pbTreeStyleOperation.to),
-                                          attributes: pbTreeStyleOperation.attributes,
+                                          attributes: pbTreeStyleOperation.attributes, 
+                                          attributesToRemove: pbTreeStyleOperation.attributesToRemove,
                                           executedAt: fromTimeTicket(pbTreeStyleOperation.executedAt))
             } else {
                 throw YorkieError.unimplemented(message: "unimplemented operation \(pbOperation)")
diff --git a/Sources/API/V1/yorkie/v1/resources.pb.swift b/Sources/API/V1/yorkie/v1/resources.pb.swift
index b35f05ff..14cfac82 100644
--- a/Sources/API/V1/yorkie/v1/resources.pb.swift
+++ b/Sources/API/V1/yorkie/v1/resources.pb.swift
@@ -952,6 +952,11 @@ struct Yorkie_V1_Operation {
     /// Clears the value of `executedAt`. Subsequent reads from it will return its default value.
     mutating func clearExecutedAt() {_uniqueStorage()._executedAt = nil}
 
+    var attributesToRemove: [String] {
+      get {return _storage._attributesToRemove}
+      set {_uniqueStorage()._attributesToRemove = newValue}
+    }
+
     var unknownFields = SwiftProtobuf.UnknownStorage()
 
     init() {}
@@ -2533,7 +2538,15 @@ extension Yorkie_V1_Operation.Set: SwiftProtobuf.Message, SwiftProtobuf._Message
     var _value: Yorkie_V1_JSONElementSimple? = nil
     var _executedAt: Yorkie_V1_TimeTicket? = nil
 
-    static let defaultInstance = _StorageClass()
+    #if swift(>=5.10)
+      // This property is used as the initial default value for new instances of the type.
+      // The type itself is protecting the reference to its storage via CoW semantics.
+      // This will force a copy to be made of this reference when the first mutation occurs;
+      // hence, it is safe to mark this as `nonisolated(unsafe)`.
+      static nonisolated(unsafe) let defaultInstance = _StorageClass()
+    #else
+      static let defaultInstance = _StorageClass()
+    #endif
 
     private init() {}
 
@@ -2625,7 +2638,15 @@ extension Yorkie_V1_Operation.Add: SwiftProtobuf.Message, SwiftProtobuf._Message
     var _value: Yorkie_V1_JSONElementSimple? = nil
     var _executedAt: Yorkie_V1_TimeTicket? = nil
 
-    static let defaultInstance = _StorageClass()
+    #if swift(>=5.10)
+      // This property is used as the initial default value for new instances of the type.
+      // The type itself is protecting the reference to its storage via CoW semantics.
+      // This will force a copy to be made of this reference when the first mutation occurs;
+      // hence, it is safe to mark this as `nonisolated(unsafe)`.
+      static nonisolated(unsafe) let defaultInstance = _StorageClass()
+    #else
+      static let defaultInstance = _StorageClass()
+    #endif
 
     private init() {}
 
@@ -2825,7 +2846,15 @@ extension Yorkie_V1_Operation.Edit: SwiftProtobuf.Message, SwiftProtobuf._Messag
     var _executedAt: Yorkie_V1_TimeTicket? = nil
     var _attributes: Dictionary<String,String> = [:]
 
-    static let defaultInstance = _StorageClass()
+    #if swift(>=5.10)
+      // This property is used as the initial default value for new instances of the type.
+      // The type itself is protecting the reference to its storage via CoW semantics.
+      // This will force a copy to be made of this reference when the first mutation occurs;
+      // hence, it is safe to mark this as `nonisolated(unsafe)`.
+      static nonisolated(unsafe) let defaultInstance = _StorageClass()
+    #else
+      static let defaultInstance = _StorageClass()
+    #endif
 
     private init() {}
 
@@ -2993,7 +3022,15 @@ extension Yorkie_V1_Operation.Style: SwiftProtobuf.Message, SwiftProtobuf._Messa
     var _executedAt: Yorkie_V1_TimeTicket? = nil
     var _createdAtMapByActor: Dictionary<String,Yorkie_V1_TimeTicket> = [:]
 
-    static let defaultInstance = _StorageClass()
+    #if swift(>=5.10)
+      // This property is used as the initial default value for new instances of the type.
+      // The type itself is protecting the reference to its storage via CoW semantics.
+      // This will force a copy to be made of this reference when the first mutation occurs;
+      // hence, it is safe to mark this as `nonisolated(unsafe)`.
+      static nonisolated(unsafe) let defaultInstance = _StorageClass()
+    #else
+      static let defaultInstance = _StorageClass()
+    #endif
 
     private init() {}
 
@@ -3095,7 +3132,15 @@ extension Yorkie_V1_Operation.Increase: SwiftProtobuf.Message, SwiftProtobuf._Me
     var _value: Yorkie_V1_JSONElementSimple? = nil
     var _executedAt: Yorkie_V1_TimeTicket? = nil
 
-    static let defaultInstance = _StorageClass()
+    #if swift(>=5.10)
+      // This property is used as the initial default value for new instances of the type.
+      // The type itself is protecting the reference to its storage via CoW semantics.
+      // This will force a copy to be made of this reference when the first mutation occurs;
+      // hence, it is safe to mark this as `nonisolated(unsafe)`.
+      static nonisolated(unsafe) let defaultInstance = _StorageClass()
+    #else
+      static let defaultInstance = _StorageClass()
+    #endif
 
     private init() {}
 
@@ -3187,7 +3232,15 @@ extension Yorkie_V1_Operation.TreeEdit: SwiftProtobuf.Message, SwiftProtobuf._Me
     var _splitLevel: Int32 = 0
     var _executedAt: Yorkie_V1_TimeTicket? = nil
 
-    static let defaultInstance = _StorageClass()
+    #if swift(>=5.10)
+      // This property is used as the initial default value for new instances of the type.
+      // The type itself is protecting the reference to its storage via CoW semantics.
+      // This will force a copy to be made of this reference when the first mutation occurs;
+      // hence, it is safe to mark this as `nonisolated(unsafe)`.
+      static nonisolated(unsafe) let defaultInstance = _StorageClass()
+    #else
+      static let defaultInstance = _StorageClass()
+    #endif
 
     private init() {}
 
@@ -3290,6 +3343,7 @@ extension Yorkie_V1_Operation.TreeStyle: SwiftProtobuf.Message, SwiftProtobuf._M
     3: .same(proto: "to"),
     4: .same(proto: "attributes"),
     5: .standard(proto: "executed_at"),
+    6: .standard(proto: "attributes_to_remove"),
   ]
 
   fileprivate class _StorageClass {
@@ -3298,8 +3352,17 @@ extension Yorkie_V1_Operation.TreeStyle: SwiftProtobuf.Message, SwiftProtobuf._M
     var _to: Yorkie_V1_TreePos? = nil
     var _attributes: Dictionary<String,String> = [:]
     var _executedAt: Yorkie_V1_TimeTicket? = nil
-
-    static let defaultInstance = _StorageClass()
+    var _attributesToRemove: [String] = []
+
+    #if swift(>=5.10)
+      // This property is used as the initial default value for new instances of the type.
+      // The type itself is protecting the reference to its storage via CoW semantics.
+      // This will force a copy to be made of this reference when the first mutation occurs;
+      // hence, it is safe to mark this as `nonisolated(unsafe)`.
+      static nonisolated(unsafe) let defaultInstance = _StorageClass()
+    #else
+      static let defaultInstance = _StorageClass()
+    #endif
 
     private init() {}
 
@@ -3309,6 +3372,7 @@ extension Yorkie_V1_Operation.TreeStyle: SwiftProtobuf.Message, SwiftProtobuf._M
       _to = source._to
       _attributes = source._attributes
       _executedAt = source._executedAt
+      _attributesToRemove = source._attributesToRemove
     }
   }
 
@@ -3332,6 +3396,7 @@ extension Yorkie_V1_Operation.TreeStyle: SwiftProtobuf.Message, SwiftProtobuf._M
         case 3: try { try decoder.decodeSingularMessageField(value: &_storage._to) }()
         case 4: try { try decoder.decodeMapField(fieldType: SwiftProtobuf._ProtobufMap<SwiftProtobuf.ProtobufString,SwiftProtobuf.ProtobufString>.self, value: &_storage._attributes) }()
         case 5: try { try decoder.decodeSingularMessageField(value: &_storage._executedAt) }()
+        case 6: try { try decoder.decodeRepeatedStringField(value: &_storage._attributesToRemove) }()
         default: break
         }
       }
@@ -3359,6 +3424,9 @@ extension Yorkie_V1_Operation.TreeStyle: SwiftProtobuf.Message, SwiftProtobuf._M
       try { if let v = _storage._executedAt {
         try visitor.visitSingularMessageField(value: v, fieldNumber: 5)
       } }()
+      if !_storage._attributesToRemove.isEmpty {
+        try visitor.visitRepeatedStringField(value: _storage._attributesToRemove, fieldNumber: 6)
+      }
     }
     try unknownFields.traverse(visitor: &visitor)
   }
@@ -3373,6 +3441,7 @@ extension Yorkie_V1_Operation.TreeStyle: SwiftProtobuf.Message, SwiftProtobuf._M
         if _storage._to != rhs_storage._to {return false}
         if _storage._attributes != rhs_storage._attributes {return false}
         if _storage._executedAt != rhs_storage._executedAt {return false}
+        if _storage._attributesToRemove != rhs_storage._attributesToRemove {return false}
         return true
       }
       if !storagesAreEqual {return false}
@@ -3973,7 +4042,15 @@ extension Yorkie_V1_RGANode: SwiftProtobuf.Message, SwiftProtobuf._MessageImplem
     var _next: Yorkie_V1_RGANode? = nil
     var _element: Yorkie_V1_JSONElement? = nil
 
-    static let defaultInstance = _StorageClass()
+    #if swift(>=5.10)
+      // This property is used as the initial default value for new instances of the type.
+      // The type itself is protecting the reference to its storage via CoW semantics.
+      // This will force a copy to be made of this reference when the first mutation occurs;
+      // hence, it is safe to mark this as `nonisolated(unsafe)`.
+      static nonisolated(unsafe) let defaultInstance = _StorageClass()
+    #else
+      static let defaultInstance = _StorageClass()
+    #endif
 
     private init() {}
 
@@ -4205,7 +4282,15 @@ extension Yorkie_V1_TreeNode: SwiftProtobuf.Message, SwiftProtobuf._MessageImple
     var _depth: Int32 = 0
     var _attributes: Dictionary<String,Yorkie_V1_NodeAttr> = [:]
 
-    static let defaultInstance = _StorageClass()
+    #if swift(>=5.10)
+      // This property is used as the initial default value for new instances of the type.
+      // The type itself is protecting the reference to its storage via CoW semantics.
+      // This will force a copy to be made of this reference when the first mutation occurs;
+      // hence, it is safe to mark this as `nonisolated(unsafe)`.
+      static nonisolated(unsafe) let defaultInstance = _StorageClass()
+    #else
+      static let defaultInstance = _StorageClass()
+    #endif
 
     private init() {}
 
diff --git a/Sources/API/V1/yorkie/v1/resources.proto b/Sources/API/V1/yorkie/v1/resources.proto
index b98bd59b..1b186a94 100644
--- a/Sources/API/V1/yorkie/v1/resources.proto
+++ b/Sources/API/V1/yorkie/v1/resources.proto
@@ -133,6 +133,7 @@ message Operation {
     TreePos to = 3;
     map<string, string> attributes = 4;
     TimeTicket executed_at = 5;
+    repeated string attributes_to_remove = 6;
   }
 
   oneof body {
diff --git a/Sources/Document/CRDT/CRDTTree.swift b/Sources/Document/CRDT/CRDTTree.swift
index 1566b31b..ce24ba53 100644
--- a/Sources/Document/CRDT/CRDTTree.swift
+++ b/Sources/Document/CRDT/CRDTTree.swift
@@ -35,11 +35,13 @@ struct TreeNodeForTest: Codable {
 enum TreeChangeType {
     case content
     case style
+    case removeStyle
 }
 
 enum TreeChangeValue {
     case nodes([CRDTTreeNode])
     case attributes([String: String])
+    case attributesToRemove([String])
 }
 
 /**
@@ -571,28 +573,50 @@ class CRDTTree: CRDTGCElement {
      */
     @discardableResult
     func style(_ range: TreePosRange, _ attributes: [String: String]?, _ editedAt: TimeTicket) throws -> [TreeChange] {
+        try self.performChangeStyle(range, attributes, nil, editedAt)
+    }
+
+    /**
+     * `removeStyle` removes the given attributes of the given range.
+     */
+    @discardableResult
+    func removeStyle(_ range: TreePosRange, _ attributesToRemove: [String], _ editedAt: TimeTicket) throws -> [TreeChange] {
+        try self.performChangeStyle(range, nil, attributesToRemove, editedAt)
+    }
+
+    private func performChangeStyle(_ range: TreePosRange, _ attributes: [String: String]?, _ attributesToRemove: [String]?, _ editedAt: TimeTicket) throws -> [TreeChange] {
         let (fromParent, fromLeft) = try self.findNodesAndSplitText(range.0, editedAt)
         let (toParent, toLeft) = try self.findNodesAndSplitText(range.1, editedAt)
         var changes: [TreeChange] = []
 
-        var value: TreeChangeValue?
+        let value: TreeChangeValue?
+        let type: TreeChangeType
 
         if let attributes {
             value = .attributes(attributes)
+            type = .style
+        } else if let attributesToRemove {
+            value = .attributesToRemove(attributesToRemove)
+            type = .removeStyle
+        } else {
+            fatalError()
         }
 
         try self.traverseInPosRange(fromParent, fromLeft, toParent, toLeft) { token, _ in
             let (node, _) = token
-            if node.isRemoved == false, node.isText == false, let attributes {
+            if node.isRemoved == false, node.isText == false {
                 if node.attrs == nil {
                     node.attrs = RHT()
                 }
-                for (key, value) in attributes {
+                for (key, value) in attributes ?? [:] {
                     node.attrs?.set(key: key, value: value, executedAt: editedAt)
                 }
+                for key in attributesToRemove ?? [] {
+                    node.attrs?.remove(key: key, executedAt: editedAt)
+                }
 
                 try changes.append(TreeChange(actor: editedAt.actorID,
-                                              type: .style,
+                                              type: type,
                                               from: self.toIndex(fromParent, fromLeft),
                                               to: self.toIndex(toParent, toLeft),
                                               fromPath: self.toPath(fromParent, fromLeft),
diff --git a/Sources/Document/CRDT/RHT.swift b/Sources/Document/CRDT/RHT.swift
index 9cda5367..d9140a68 100644
--- a/Sources/Document/CRDT/RHT.swift
+++ b/Sources/Document/CRDT/RHT.swift
@@ -23,6 +23,7 @@ struct RHTNode {
     var key: String
     var value: String
     var updatedAt: TimeTicket
+    var isRemoved: Bool
 }
 
 /**
@@ -31,26 +32,62 @@ struct RHTNode {
  */
 class RHT {
     private var nodeMapByKey = [String: RHTNode]()
+    private var numberOfRemovedElement: Int = 0
 
     /**
      * `set` sets the value of the given key.
      */
     func set(key: String, value: String, executedAt: TimeTicket) {
-        let previous = self.nodeMapByKey[key]
+        if let prev = nodeMapByKey[key] {
+            if executedAt.after(prev.updatedAt) {
+                if !prev.isRemoved {
+                    self.numberOfRemovedElement -= 1
+                }
+                let node = RHTNode(key: key, value: value, updatedAt: executedAt, isRemoved: false)
+                self.nodeMapByKey[key] = node
+            }
+        } else {
+            let node = RHTNode(key: key, value: value, updatedAt: executedAt, isRemoved: false)
+            self.nodeMapByKey[key] = node
+        }
+    }
+
+    /**
+     * `remove` removes the Element of the given key.
+     */
+    @discardableResult
+    func remove(key: String, executedAt: TimeTicket) -> String {
+        guard let prev = self.nodeMapByKey[key] else {
+            self.numberOfRemovedElement += 1
+            let node = RHTNode(key: key, value: "", updatedAt: executedAt, isRemoved: true)
+            self.nodeMapByKey[key] = node
+
+            return ""
+        }
+
+        if executedAt.after(prev.updatedAt) {
+            let alreadyRemoved = prev.isRemoved
+            if !alreadyRemoved {
+                self.numberOfRemovedElement += 1
+            }
+            let node = RHTNode(key: key, value: prev.value, updatedAt: executedAt, isRemoved: true)
+            self.nodeMapByKey[key] = node
 
-        if let previous, executedAt.after(previous.updatedAt) == false {
-            return
+            if alreadyRemoved {
+                return ""
+            }
+
+            return prev.value
         }
 
-        let node = RHTNode(key: key, value: value, updatedAt: executedAt)
-        self.nodeMapByKey[key] = node
+        return ""
     }
 
     /**
      * `has` returns whether the element exists of the given key or not.
      */
     func has(key: String) -> Bool {
-        return self.nodeMapByKey[key] != nil
+        !(self.nodeMapByKey[key]?.isRemoved ?? true)
     }
 
     /**
@@ -86,7 +123,7 @@ class RHT {
             result.append("\"\(key)\":\"\(node.value.escaped())\"")
         }
 
-        return result.isEmpty ? "" : "{\(result.joined(separator: ","))}"
+        return result.isEmpty ? "{}" : "{\(result.joined(separator: ","))}"
     }
 
     /**
@@ -100,7 +137,7 @@ class RHT {
         let sortedKeys = self.nodeMapByKey.keys.sorted()
 
         let xmlAttributes = sortedKeys.compactMap { key in
-            if let value = self.nodeMapByKey[key] {
+            if let value = self.nodeMapByKey[key], value.isRemoved == false {
                 return "\(key)=\"\(value.value)\""
             } else {
                 return nil
@@ -114,7 +151,7 @@ class RHT {
      * `size` returns the size of RHT
      */
     public var size: Int {
-        self.nodeMapByKey.count
+        self.nodeMapByKey.count - self.numberOfRemovedElement
     }
 
     /**
@@ -122,7 +159,7 @@ class RHT {
      */
     func toObject() -> [String: (value: String, updatedAt: TimeTicket)] {
         var result = [String: (String, TimeTicket)]()
-        for (key, node) in self.nodeMapByKey {
+        for (key, node) in self.nodeMapByKey.filter({ _, node in !node.isRemoved }) {
             result[key] = (node.value, node.updatedAt)
         }
 
diff --git a/Sources/Document/Json/JSONTree.swift b/Sources/Document/Json/JSONTree.swift
index f9e6e6eb..442b8f83 100644
--- a/Sources/Document/Json/JSONTree.swift
+++ b/Sources/Document/Json/JSONTree.swift
@@ -336,6 +336,7 @@ public class JSONTree {
                                                    fromPos: fromPos,
                                                    toPos: toPos,
                                                    attributes: stringAttrs,
+                                                   attributesToRemove: [],
                                                    executedAt: ticket)
         )
     }
@@ -370,6 +371,34 @@ public class JSONTree {
                                                    fromPos: fromPos,
                                                    toPos: toPos,
                                                    attributes: stringAttrs,
+                                                   attributesToRemove: [],
+                                                   executedAt: ticket)
+        )
+    }
+
+    /**
+     * `removeStyle` removes the attributes to the elements of the given range.
+     */
+    public func removeStyle(_ fromIdx: Int, _ toIdx: Int, _ attributesToRemove: [String]) throws {
+        guard let context, let tree else {
+            throw YorkieError.unexpected(message: "it is not initialized yet")
+        }
+
+        if fromIdx > toIdx {
+            throw YorkieError.unexpected(message: "from should be less than or equal to to")
+        }
+
+        let fromPos = try tree.findPos(fromIdx)
+        let toPos = try tree.findPos(toIdx)
+        let ticket = context.issueTimeTicket
+
+        try tree.removeStyle((fromPos, toPos), attributesToRemove, ticket)
+
+        context.push(operation: TreeStyleOperation(parentCreatedAt: tree.createdAt,
+                                                   fromPos: fromPos,
+                                                   toPos: toPos,
+                                                   attributes: [:],
+                                                   attributesToRemove: attributesToRemove,
                                                    executedAt: ticket)
         )
     }
diff --git a/Sources/Document/Operation/TreeSytleOperation.swift b/Sources/Document/Operation/TreeSytleOperation.swift
index 711096d5..fe8f366e 100644
--- a/Sources/Document/Operation/TreeSytleOperation.swift
+++ b/Sources/Document/Operation/TreeSytleOperation.swift
@@ -36,12 +36,14 @@ class TreeStyleOperation: Operation {
      * `attributes` returns the content of Edit.
      */
     let attributes: [String: String]
+    let attributesToRemove: [String]
 
-    init(parentCreatedAt: TimeTicket, fromPos: CRDTTreePos, toPos: CRDTTreePos, attributes: [String: String], executedAt: TimeTicket) {
+    init(parentCreatedAt: TimeTicket, fromPos: CRDTTreePos, toPos: CRDTTreePos, attributes: [String: String], attributesToRemove: [String], executedAt: TimeTicket) {
         self.parentCreatedAt = parentCreatedAt
         self.fromPos = fromPos
         self.toPos = toPos
         self.attributes = attributes
+        self.attributesToRemove = attributesToRemove
         self.executedAt = executedAt
     }
 
@@ -60,7 +62,13 @@ class TreeStyleOperation: Operation {
             fatalError("fail to execute, only Tree can execute edit")
         }
 
-        let changes = try tree.style((self.fromPos, self.toPos), self.attributes, self.executedAt)
+        let changes: [TreeChange]
+
+        if self.attributes.isEmpty == false {
+            changes = try tree.style((self.fromPos, self.toPos), self.attributes, self.executedAt)
+        } else {
+            changes = try tree.removeStyle((self.fromPos, self.toPos), self.attributesToRemove, self.executedAt)
+        }
 
         guard let path = try? root.createPath(createdAt: parentCreatedAt) else {
             throw YorkieError.unexpected(message: "fail to get path")
diff --git a/Sources/Document/Time/TimeTicket.swift b/Sources/Document/Time/TimeTicket.swift
index b4cd4352..126e8c1f 100644
--- a/Sources/Document/Time/TimeTicket.swift
+++ b/Sources/Document/Time/TimeTicket.swift
@@ -28,7 +28,8 @@ public struct TimeTicket: Comparable {
     }
 
     public static let initial = TimeTicket(lamport: 0, delimiter: Values.initialDelimiter, actorID: ActorIDs.initial)
-    static let max = TimeTicket(lamport: Values.maxLamport, delimiter: Values.maxDelemiter, actorID: ActorIDs.max)
+    public static let next = TimeTicket(lamport: 1, delimiter: Values.initialDelimiter + 1, actorID: ActorIDs.initial)
+    public static let max = TimeTicket(lamport: Values.maxLamport, delimiter: Values.maxDelemiter, actorID: ActorIDs.max)
 
     /**
      * `lamport` returns the lamport int64.
diff --git a/Tests/Integration/ClientIntegrationTests.swift b/Tests/Integration/ClientIntegrationTests.swift
index f377afd4..8a0a4454 100644
--- a/Tests/Integration/ClientIntegrationTests.swift
+++ b/Tests/Integration/ClientIntegrationTests.swift
@@ -219,11 +219,17 @@ final class ClientIntegrationTests: XCTestCase {
             StreamConnectionStatus.disconnected
         ]
 
+        let exp = self.expectation(description: "exp")
+
         c1.eventStream.sink { event in
             switch event {
             case let event as StreamConnectionStatusChangedEvent:
                 XCTAssertEqual(event.value, c1ExpectedValues[c1NumberOfEvents])
                 c1NumberOfEvents += 1
+
+                if c1NumberOfEvents == c1ExpectedValues.count {
+                    exp.fulfill()
+                }
             default:
                 break
             }
@@ -238,6 +244,8 @@ final class ClientIntegrationTests: XCTestCase {
         try await c1.detach(d1)
 
         try await c1.deactivate()
+
+        await fulfillment(of: [exp], timeout: 10)
     }
 
     func test_should_apply_previous_changes_when_resuming_document() async throws {
@@ -517,7 +525,7 @@ final class ClientIntegrationTests: XCTestCase {
         // but a response has not yet been received.
         try await c2.sync()
 
-        await fulfillment(of: [expect3])
+        await fulfillment(of: [expect3], timeout: 10)
 
         try await d2.update { root, _ in
             try (root.t as? JSONTree)?.edit(2, 2, JSONTreeTextNode(value: "b"))
diff --git a/Tests/Integration/TreeIntegrationTests.swift b/Tests/Integration/TreeIntegrationTests.swift
index a4051311..c144bc32 100644
--- a/Tests/Integration/TreeIntegrationTests.swift
+++ b/Tests/Integration/TreeIntegrationTests.swift
@@ -1012,6 +1012,41 @@ final class TreeIntegrationStyleTests: XCTestCase {
         }
     }
 
+    func test_can_sync_its_content_with_remove_style() async throws {
+        try await withTwoClientsAndDocuments(self.description) { c1, d1, c2, d2 in
+            try await d1.update { root, _ in
+                root.t = JSONTree(initialRoot:
+                    JSONTreeElementNode(type: "doc",
+                                        children: [JSONTreeElementNode(type: "p",
+                                                                       children: [JSONTreeTextNode(value: "hello")],
+                                                                       attributes: ["italic": "true"])])
+                )
+            }
+
+            try await c1.sync()
+            try await c2.sync()
+
+            var d1XML = await(d1.getRoot().t as? JSONTree)?.toXML()
+            var d2XML = await(d2.getRoot().t as? JSONTree)?.toXML()
+
+            XCTAssertEqual(d1XML, /* html */ "<doc><p italic=\"true\">hello</p></doc>")
+            XCTAssertEqual(d2XML, /* html */ "<doc><p italic=\"true\">hello</p></doc>")
+
+            try await d1.update { root, _ in
+                try (root.t as? JSONTree)?.removeStyle(0, 1, ["italic"])
+            }
+
+            try await c1.sync()
+            try await c2.sync()
+
+            d1XML = await(d1.getRoot().t as? JSONTree)?.toXML()
+            d2XML = await(d2.getRoot().t as? JSONTree)?.toXML()
+
+            XCTAssertEqual(d1XML, /* html */ "<doc><p>hello</p></doc>")
+            XCTAssertEqual(d2XML, /* html */ "<doc><p>hello</p></doc>")
+        }
+    }
+
     func test_should_return_correct_range_path_within_doc_subscribe() async throws {
         try await withTwoClientsAndDocuments(self.description) { c1, d1, c2, d2 in
             try await d1.update { root, _ in
diff --git a/Tests/Unit/Document/CRDT/RHTTests.swift b/Tests/Unit/Document/CRDT/RHTTests.swift
index 5bca9563..260f110c 100644
--- a/Tests/Unit/Document/CRDT/RHTTests.swift
+++ b/Tests/Unit/Document/CRDT/RHTTests.swift
@@ -25,7 +25,7 @@ class RHTTests: XCTestCase {
 
         let rht = RHT()
 
-        XCTAssertEqual(rht.toJSON(), "")
+        XCTAssertEqual(rht.toJSON(), "{}")
 
         rht.set(key: testKey, value: testValue, executedAt: TimeTicket.initial)
 
@@ -36,6 +36,24 @@ class RHTTests: XCTestCase {
         XCTAssertEqual(notExistsValue, nil)
     }
 
+    func test_should_handle_remove() throws {
+        let testKey = "test-key"
+        let testValue = "test-value"
+
+        let rht = RHT()
+
+        XCTAssertEqual(rht.toJSON(), "{}")
+        rht.set(key: testKey, value: testValue, executedAt: TimeTicket.initial)
+
+        let actualValue = try rht.get(key: testKey)
+        XCTAssertEqual(actualValue, testValue)
+        XCTAssertEqual(rht.size, 1)
+
+        rht.remove(key: testKey, executedAt: TimeTicket.next)
+        XCTAssertEqual(rht.has(key: testKey), false)
+        XCTAssertEqual(rht.size, 0)
+    }
+
     func test_should_not_set_when_same_key_exsits_and_updatedAt_is_bigger() {
         let actorId = "actorId-1"
         let testKey = "test-key"
@@ -43,7 +61,7 @@ class RHTTests: XCTestCase {
 
         let rht = RHT()
 
-        XCTAssertEqual(rht.toJSON(), "")
+        XCTAssertEqual(rht.toJSON(), "{}")
 
         rht.set(key: testKey,
                 value: testValue,
@@ -66,7 +84,7 @@ class RHTTests: XCTestCase {
         let rht = RHT()
 
         // Check if a rht object is constructed well.
-        XCTAssertEqual(rht.toJSON(), "")
+        XCTAssertEqual(rht.toJSON(), "{}")
 
         let notExistsValue = try? rht.get(key: notExistsKey)
         XCTAssertEqual(notExistsValue, nil)
@@ -79,7 +97,7 @@ class RHTTests: XCTestCase {
         let rht = RHT()
 
         // Check if a rht object is constructed well.
-        XCTAssertEqual(rht.toJSON(), "")
+        XCTAssertEqual(rht.toJSON(), "{}")
 
         rht.set(key: testKey, value: testValue, executedAt: TimeTicket.initial)
 
diff --git a/Tests/Unit/Document/JSONTextTest.swift b/Tests/Unit/Document/JSONTextTest.swift
index f6b66339..36bc1d4c 100644
--- a/Tests/Unit/Document/JSONTextTest.swift
+++ b/Tests/Unit/Document/JSONTextTest.swift
@@ -132,7 +132,7 @@ final class JSONTextTest: XCTestCase {
                 (root.text as? JSONText)?.edit(cmd.from, cmd.to, cmd.content)
             }
 
-            await fulfillment(of: [commands[index].exp], timeout: 1_000_000_000)
+            await fulfillment(of: [commands[index].exp], timeout: 2)
 
             let text = await(doc.getRoot()["text"] as? JSONText)?.toString
             XCTAssertEqual(view.toString, text)