diff --git a/.claude/settings.local.json b/.claude/settings.local.json
new file mode 100644
index 0000000..4f9167d
--- /dev/null
+++ b/.claude/settings.local.json
@@ -0,0 +1,8 @@
+{
+  "enableAllProjectMcpServers": false,
+  "permissions": {
+    "allow": [
+      "Bash(find:*)"
+    ]
+  }
+}
\ No newline at end of file
diff --git a/CommandForgeGenerator.Tests/GenerateTestCode.cs b/CommandForgeGenerator.Tests/GenerateTestCode.cs
new file mode 100644
index 0000000..d0e1db9
--- /dev/null
+++ b/CommandForgeGenerator.Tests/GenerateTestCode.cs
@@ -0,0 +1,40 @@
+namespace CommandForgeGenerator.Tests;
+
+public class GenerateTestCode
+{
+    public const string TextCommand = """
+                                      #if ENABLE_COMMAND_FORGE_GENERATOR
+                                      namespace CommandForgeGenerator.Command
+                                      {
+                                          public partial class TextCommand : ICommandForgeCommand
+                                          {
+                                              public const string Type = "text";
+                                              public readonly CommandId CommandId;
+                                              
+                                              public readonly string Character;
+                                              public readonly string Body;
+                                              
+                                        
+                                              public static TextCommand Create(int commandId, global::Newtonsoft.Json.Linq.JToken json)
+                                              {
+                                                  
+                                                  var Character = (string)json["character"];
+                                                  var Body = (string)json["body"];
+                                                  
+                                                  
+                                                  return new TextCommand(commandId, Character, Body);
+                                              }
+                                              
+                                              public TextCommand(int commandId, string Character, string Body)
+                                              {
+                                                  CommandId = (CommandId)commandId;
+                                                  
+                                              this.Character = Character;
+                                              this.Body = Body;
+                                              
+                                              }
+                                          }
+                                      }
+                                      #endif
+                                      """;
+}
\ No newline at end of file
diff --git a/CommandForgeGenerator.Tests/Test.cs b/CommandForgeGenerator.Tests/Test.cs
index 976db08..2d2ba98 100644
--- a/CommandForgeGenerator.Tests/Test.cs
+++ b/CommandForgeGenerator.Tests/Test.cs
@@ -1,4 +1,5 @@
 using System.IO;
+using System.Linq;
 using CommandForgeGenerator.Generator.CodeGenerate;
 using CommandForgeGenerator.Generator.Json;
 using CommandForgeGenerator.Generator.Semantic;
@@ -64,6 +65,7 @@ public void GenerateTest()
         var codeFiles = CodeGenerator.Generate(commandsSchema);
         
         Assert.Equal(16, codeFiles.Count);
+        Assert.Equal(GenerateTestCode.TextCommand, codeFiles.FirstOrDefault(c => c.FileName == "TextCommand.g.cs").Code);
         
         #region Internal
         
@@ -84,7 +86,6 @@ string GetSampleYaml()
                          body:
                            type: string
                            multiline: true
-                           required: true
                    
                      - id: emote
                        label: エモート
diff --git a/CommandForgeGenerator/CodeGenerate/CodeGenerator.cs b/CommandForgeGenerator/CodeGenerate/CodeGenerator.cs
index 72a07ce..745938c 100644
--- a/CommandForgeGenerator/CodeGenerate/CodeGenerator.cs
+++ b/CommandForgeGenerator/CodeGenerate/CodeGenerator.cs
@@ -101,7 +101,7 @@ private static string GeneratePropertiesCode(List<CommandProperty> commandProper
         properties.AppendLine();
         foreach (var property in commandProperties)
         {
-            var type = GetTypeCode(property.Type);
+            var type = GetTypeCode(property.Type, property.IsRequired);
             properties.AppendLine($"public readonly {type} {property.CodeProperty};");
         }
         
@@ -114,39 +114,82 @@ private static string GenerateCreateMethodTempVariables(List<CommandProperty> co
         properties.AppendLine();
         foreach (var property in commandProperties)
         {
-            var type = GetTypeCode(property.Type);
-            if (property.Type is CommandPropertyType.CommandId)
-            {
-                properties.AppendLine($"var {property.CodeProperty} = (CommandId)((int)json[\"{property.Name}\"]);");
-            }
-            else if (property.Type is CommandPropertyType.Vector2)
-            {
-                properties.AppendLine($"var {property.CodeProperty}Array = json[\"{property.Name}\"];");
-                properties.AppendLine($"var {property.CodeProperty} = new global::UnityEngine.Vector2((float){property.CodeProperty}Array[0], (float){property.CodeProperty}Array[1]);");
-            }
-            else if (property.Type is CommandPropertyType.Vector3)
-            {
-                properties.AppendLine($"var {property.CodeProperty}Array = json[\"{property.Name}\"];");
-                properties.AppendLine($"var {property.CodeProperty} = new global::UnityEngine.Vector3((float){property.CodeProperty}Array[0], (float){property.CodeProperty}Array[1], (float){property.CodeProperty}Array[2]);");
-            }
-            else if (property.Type is CommandPropertyType.Vector4)
-            {
-                properties.AppendLine($"var {property.CodeProperty}Array = json[\"{property.Name}\"];");
-                properties.AppendLine($"var {property.CodeProperty} = new global::UnityEngine.Vector4((float){property.CodeProperty}Array[0], (float){property.CodeProperty}Array[1], (float){property.CodeProperty}Array[2], (float){property.CodeProperty}Array[3]);");
-            }
-            else if (property.Type is CommandPropertyType.Vector2Int)
-            {
-                properties.AppendLine($"var {property.CodeProperty}Array = json[\"{property.Name}\"];");
-                properties.AppendLine($"var {property.CodeProperty} = new global::UnityEngine.Vector2Int((int){property.CodeProperty}Array[0], (int){property.CodeProperty}Array[1]);");
-            }
-            else if (property.Type is CommandPropertyType.Vector3Int)
+            var type = GetTypeCode(property.Type, property.IsRequired);
+            
+            if (property.IsRequired)
             {
-                properties.AppendLine($"var {property.CodeProperty}Array = json[\"{property.Name}\"];");
-                properties.AppendLine($"var {property.CodeProperty} = new global::UnityEngine.Vector3Int((int){property.CodeProperty}Array[0], (int){property.CodeProperty}Array[1], (int){property.CodeProperty}Array[2]);");
+                // required の場合は従来通り
+                if (property.Type is CommandPropertyType.CommandId)
+                {
+                    properties.AppendLine($"var {property.CodeProperty} = (CommandId)((int)json[\"{property.Name}\"]);");
+                }
+                else if (property.Type is CommandPropertyType.Vector2)
+                {
+                    properties.AppendLine($"var {property.CodeProperty}Array = json[\"{property.Name}\"];");
+                    properties.AppendLine($"var {property.CodeProperty} = new global::UnityEngine.Vector2((float){property.CodeProperty}Array[0], (float){property.CodeProperty}Array[1]);");
+                }
+                else if (property.Type is CommandPropertyType.Vector3)
+                {
+                    properties.AppendLine($"var {property.CodeProperty}Array = json[\"{property.Name}\"];");
+                    properties.AppendLine($"var {property.CodeProperty} = new global::UnityEngine.Vector3((float){property.CodeProperty}Array[0], (float){property.CodeProperty}Array[1], (float){property.CodeProperty}Array[2]);");
+                }
+                else if (property.Type is CommandPropertyType.Vector4)
+                {
+                    properties.AppendLine($"var {property.CodeProperty}Array = json[\"{property.Name}\"];");
+                    properties.AppendLine($"var {property.CodeProperty} = new global::UnityEngine.Vector4((float){property.CodeProperty}Array[0], (float){property.CodeProperty}Array[1], (float){property.CodeProperty}Array[2], (float){property.CodeProperty}Array[3]);");
+                }
+                else if (property.Type is CommandPropertyType.Vector2Int)
+                {
+                    properties.AppendLine($"var {property.CodeProperty}Array = json[\"{property.Name}\"];");
+                    properties.AppendLine($"var {property.CodeProperty} = new global::UnityEngine.Vector2Int((int){property.CodeProperty}Array[0], (int){property.CodeProperty}Array[1]);");
+                }
+                else if (property.Type is CommandPropertyType.Vector3Int)
+                {
+                    properties.AppendLine($"var {property.CodeProperty}Array = json[\"{property.Name}\"];");
+                    properties.AppendLine($"var {property.CodeProperty} = new global::UnityEngine.Vector3Int((int){property.CodeProperty}Array[0], (int){property.CodeProperty}Array[1], (int){property.CodeProperty}Array[2]);");
+                }
+                else
+                {
+                    properties.AppendLine($"var {property.CodeProperty} = ({type})json[\"{property.Name}\"];");
+                }
             }
             else
             {
-                properties.AppendLine($"var {property.CodeProperty} = ({type})json[\"{property.Name}\"];");
+                // nullable の場合はnullチェックを追加
+                properties.AppendLine($"var {property.CodeProperty}Token = json[\"{property.Name}\"];");
+                
+                if (property.Type is CommandPropertyType.CommandId)
+                {
+                    properties.AppendLine($"{type} {property.CodeProperty} = {property.CodeProperty}Token?.Type == global::Newtonsoft.Json.Linq.JTokenType.Null ? null : (CommandId?)((int){property.CodeProperty}Token);");
+                }
+                else if (property.Type is CommandPropertyType.Vector2)
+                {
+                    properties.AppendLine($"{type} {property.CodeProperty} = {property.CodeProperty}Token?.Type == global::Newtonsoft.Json.Linq.JTokenType.Null ? null : new global::UnityEngine.Vector2((float){property.CodeProperty}Token[0], (float){property.CodeProperty}Token[1]);");
+                }
+                else if (property.Type is CommandPropertyType.Vector3)
+                {
+                    properties.AppendLine($"{type} {property.CodeProperty} = {property.CodeProperty}Token?.Type == global::Newtonsoft.Json.Linq.JTokenType.Null ? null : new global::UnityEngine.Vector3((float){property.CodeProperty}Token[0], (float){property.CodeProperty}Token[1], (float){property.CodeProperty}Token[2]);");
+                }
+                else if (property.Type is CommandPropertyType.Vector4)
+                {
+                    properties.AppendLine($"{type} {property.CodeProperty} = {property.CodeProperty}Token?.Type == global::Newtonsoft.Json.Linq.JTokenType.Null ? null : new global::UnityEngine.Vector4((float){property.CodeProperty}Token[0], (float){property.CodeProperty}Token[1], (float){property.CodeProperty}Token[2], (float){property.CodeProperty}Token[3]);");
+                }
+                else if (property.Type is CommandPropertyType.Vector2Int)
+                {
+                    properties.AppendLine($"{type} {property.CodeProperty} = {property.CodeProperty}Token?.Type == global::Newtonsoft.Json.Linq.JTokenType.Null ? null : new global::UnityEngine.Vector2Int((int){property.CodeProperty}Token[0], (int){property.CodeProperty}Token[1]);");
+                }
+                else if (property.Type is CommandPropertyType.Vector3Int)
+                {
+                    properties.AppendLine($"{type} {property.CodeProperty} = {property.CodeProperty}Token?.Type == global::Newtonsoft.Json.Linq.JTokenType.Null ? null : new global::UnityEngine.Vector3Int((int){property.CodeProperty}Token[0], (int){property.CodeProperty}Token[1], (int){property.CodeProperty}Token[2]);");
+                }
+                else if (property.Type is CommandPropertyType.String)
+                {
+                    properties.AppendLine($"{type} {property.CodeProperty} = {property.CodeProperty}Token?.Type == global::Newtonsoft.Json.Linq.JTokenType.Null ? null : (string?){property.CodeProperty}Token;");
+                }
+                else
+                {
+                    properties.AppendLine($"{type} {property.CodeProperty} = {property.CodeProperty}Token?.Type == global::Newtonsoft.Json.Linq.JTokenType.Null ? null : ({type}){property.CodeProperty}Token;");
+                }
             }
         }
         
@@ -169,7 +212,7 @@ public static string GenerateConstructorPropertiesCode(List<CommandProperty> com
         var properties = new StringBuilder();
         foreach (var property in commandProperties)
         {
-            var type = GetTypeCode(property.Type);
+            var type = GetTypeCode(property.Type, property.IsRequired);
             properties.Append($", {type} {property.CodeProperty}");
             
         }
@@ -189,9 +232,9 @@ private static string GenerateConstructSetPropertiesCode(List<CommandProperty> c
         return construct.ToString();
     }
     
-    private static string GetTypeCode(CommandPropertyType type)
+    private static string GetTypeCode(CommandPropertyType type, bool isRequired)
     {
-        return type switch
+        var baseType = type switch
         {
             CommandPropertyType.String => "string",
             CommandPropertyType.Int => "int",
@@ -205,6 +248,20 @@ private static string GetTypeCode(CommandPropertyType type)
             CommandPropertyType.Vector3Int => "global::UnityEngine.Vector3Int",
             _ => throw new ArgumentOutOfRangeException(nameof(type), type, null)
         };
+        
+        // 値型でrequiredでない場合は nullable にする
+        if (!isRequired && type != CommandPropertyType.String)
+        {
+            return baseType + "?";
+        }
+        
+        // 参照型でも明示的に nullable にする（C# 8.0以降）
+        if (!isRequired && type == CommandPropertyType.String)
+        {
+            return baseType + "?";
+        }
+        
+        return baseType;
     }
     
     public static string GenerateLoaderCode(CommandsSemantics commandsSemantics)
diff --git a/CommandForgeGenerator/Semantic/CommandSemanticsLoader.cs b/CommandForgeGenerator/Semantic/CommandSemanticsLoader.cs
index 89f39d5..cd8cdda 100644
--- a/CommandForgeGenerator/Semantic/CommandSemanticsLoader.cs
+++ b/CommandForgeGenerator/Semantic/CommandSemanticsLoader.cs
@@ -90,7 +90,14 @@ CommandsSemantics ParseCommandsSchema(JsonObject root)
                         _ => throw new Exception($"未知の property type \"{typeStr}\"")
                     };
                     
-                    properties.Add(new CommandProperty(mappedType, propName));
+                    // required フィールドを読み取る
+                    var isRequired = true;
+                    if (propObj.Nodes.ContainsKey("required") && propObj["required"] is JsonBoolean requiredNode)
+                    {
+                        isRequired = requiredNode.Literal;
+                    }
+                    
+                    properties.Add(new CommandProperty(mappedType, propName, isRequired));
                 }
                 
                 commands.Add(new CommandSemantics(commandName, properties));
diff --git a/CommandForgeGenerator/Semantic/CommandsSemantics.cs b/CommandForgeGenerator/Semantic/CommandsSemantics.cs
index 3c2e413..1fa7c4b 100644
--- a/CommandForgeGenerator/Semantic/CommandsSemantics.cs
+++ b/CommandForgeGenerator/Semantic/CommandsSemantics.cs
@@ -28,13 +28,15 @@ public CommandSemantics(string name, List<CommandProperty> properties)
 public class CommandProperty{
     public readonly string Name;
     public readonly CommandPropertyType Type;
+    public readonly bool IsRequired;
     
     public string CodeProperty => Name.ToUpper(0);
 
-    public CommandProperty(CommandPropertyType type, string name)
+    public CommandProperty(CommandPropertyType type, string name, bool isRequired)
     {
         Type = type;
         Name = name;
+        IsRequired = isRequired;
     }
 
 }
diff --git a/CommandForgeGenerator/Semantic/ReservedCommandSemantics.cs b/CommandForgeGenerator/Semantic/ReservedCommandSemantics.cs
index 46727e7..0969cdd 100644
--- a/CommandForgeGenerator/Semantic/ReservedCommandSemantics.cs
+++ b/CommandForgeGenerator/Semantic/ReservedCommandSemantics.cs
@@ -8,8 +8,8 @@ public static List<CommandSemantics> GetReservedCommand()
     {
         var groupStart = new CommandSemantics("group_start", new List<CommandProperty>()
         {
-            new(CommandPropertyType.String, "groupName"),
-            new(CommandPropertyType.Bool, "isCollapsed"),
+            new(CommandPropertyType.String, "groupName", true),
+            new(CommandPropertyType.Bool, "isCollapsed", true),
         });
         var groupEnd = new CommandSemantics("group_end", new List<CommandProperty>());
         return new List<CommandSemantics>(){groupStart, groupEnd};