diff --git a/CommandForgeGenerator/CodeGenerate/CodeGenerator.cs b/CommandForgeGenerator/CodeGenerate/CodeGenerator.cs
index 72a07ce..913e79b 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 +114,85 @@ 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
+                if (property.Type is CommandPropertyType.String)
+                {
+                    properties.AppendLine($"var {property.CodeProperty} = json[\"{property.Name}\"] == null ? null : (string)json[\"{property.Name}\"];");
+                }
+                else if (property.Type is CommandPropertyType.CommandId)
+                {
+                    properties.AppendLine($"var {property.CodeProperty} = json[\"{property.Name}\"] == null ? null : (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} = {property.CodeProperty}Array == null ? null : 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} = {property.CodeProperty}Array == null ? null : 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} = {property.CodeProperty}Array == null ? null : 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} = {property.CodeProperty}Array == null ? null : 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} = {property.CodeProperty}Array == null ? null : 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} = json[\"{property.Name}\"] == null ? null : ({type})json[\"{property.Name}\"];");
+                }
             }
         }
         
@@ -169,7 +215,7 @@ 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 +235,9 @@ 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 +251,20 @@ 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/CommandForgeGenerator.csproj b/CommandForgeGenerator/CommandForgeGenerator.csproj
index 2110196..be65098 100644
--- a/CommandForgeGenerator/CommandForgeGenerator.csproj
+++ b/CommandForgeGenerator/CommandForgeGenerator.csproj
@@ -18,7 +18,7 @@
         <!-- NuGet Package Metadata -->
         <Title>CommandForge Generator</Title>
         <Authors>Moorestech</Authors>
-        <Version>1.0.6</Version>
+        <Version>1.0.5</Version>
         <Description>CommandForgeEditorのcommands.yamlのC#コードを生成するSourceGenerator</Description>
         <PackageProjectUrl>https://github.com/moorestech/CommandForgeGenerator</PackageProjectUrl>
         <RepositoryUrl>https://github.com/moorestech/CommandForgeGenerator</RepositoryUrl>
diff --git a/CommandForgeGenerator/Semantic/CommandSemanticsLoader.cs b/CommandForgeGenerator/Semantic/CommandSemanticsLoader.cs
index 89f39d5..01d1500 100644
--- a/CommandForgeGenerator/Semantic/CommandSemanticsLoader.cs
+++ b/CommandForgeGenerator/Semantic/CommandSemanticsLoader.cs
@@ -90,7 +90,23 @@ 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（デフォルトはfalse）
+                    var isRequired = false;
+                    if (propObj.Nodes.ContainsKey("required"))
+                    {
+                        var requiredVal = propObj["required"];
+                        if (requiredVal is JsonBoolean requiredBool)
+                        {
+                            isRequired = requiredBool.Literal;
+                        }
+                        else if (requiredVal is JsonString requiredStr)
+                        {
+                            // YAMLが文字列としてbooleanを返す場合がある
+                            isRequired = requiredStr.Literal.ToLowerInvariant() == "true";
+                        }
+                    }
+                    
+                    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};