diff --git a/Assets/VRM10/Runtime/Migration/MigrationCheck.cs b/Assets/VRM10/Runtime/Migration/MigrationCheck.cs
index 31629d9a2..57153aff6 100644
--- a/Assets/VRM10/Runtime/Migration/MigrationCheck.cs
+++ b/Assets/VRM10/Runtime/Migration/MigrationCheck.cs
@@ -7,7 +7,7 @@ namespace UniVRM10
     /// <summary>
     /// for UnitTest
     /// </summary>
-    public static class MigrationCheck
+    internal static class MigrationCheck
     {
         #region for UnitTest
         public class MigrationException : Exception
diff --git a/Assets/VRM10/Runtime/Migration/MigrationException.cs b/Assets/VRM10/Runtime/Migration/MigrationException.cs
index 4c3c4511b..641727b8c 100644
--- a/Assets/VRM10/Runtime/Migration/MigrationException.cs
+++ b/Assets/VRM10/Runtime/Migration/MigrationException.cs
@@ -2,7 +2,7 @@
 
 namespace UniVRM10
 {
-    public class MigrationException : Exception
+    internal class MigrationException : Exception
     {
         public MigrationException(string key, string value) : base($"{key}: {value}")
         {
diff --git a/Assets/VRM10/Runtime/Migration/MigrationMaterials.cs b/Assets/VRM10/Runtime/Migration/MigrationMaterials.cs
index 18254310c..5b3ffc619 100644
--- a/Assets/VRM10/Runtime/Migration/MigrationMaterials.cs
+++ b/Assets/VRM10/Runtime/Migration/MigrationMaterials.cs
@@ -10,7 +10,7 @@ namespace UniVRM10
     /// VRM 拡張に含まれる Material 情報を用いて、マイグレーションを行う.
     /// 前提として、glTF の仕様の範囲で glTFMaterial は既に読み込み済みであると仮定する.
     /// </summary>
-    public static class MigrationMaterials
+    internal static class MigrationMaterials
     {
         private const string DontUseExtensionShaderName = "VRM_USE_GLTFSHADER";
         private const string MaterialPropertiesKey = "materialProperties";
diff --git a/Assets/VRM10/Runtime/Migration/MigrationVector3.cs b/Assets/VRM10/Runtime/Migration/MigrationVector3.cs
index 1587e300b..5ed47bbbe 100644
--- a/Assets/VRM10/Runtime/Migration/MigrationVector3.cs
+++ b/Assets/VRM10/Runtime/Migration/MigrationVector3.cs
@@ -2,7 +2,7 @@ using UniJSON;
 
 namespace UniVRM10
 {
-    public static class MigrateVector3
+    internal static class MigrateVector3
     {
         /// <summary>
         /// VRM0は本来 (x, y, -z) と座標変換するべきところをしていない。
diff --git a/Assets/VRM10/Runtime/Migration/MigrationVrm.cs b/Assets/VRM10/Runtime/Migration/MigrationVrm.cs
index 5d20f28d7..b4bc5e288 100644
--- a/Assets/VRM10/Runtime/Migration/MigrationVrm.cs
+++ b/Assets/VRM10/Runtime/Migration/MigrationVrm.cs
@@ -1,15 +1,19 @@
-using System;
+using System.Runtime.CompilerServices;
+using System;
 using System.Collections.Generic;
 using UniGLTF;
 using UniJSON;
 using Unity.Collections;
 
+[assembly: InternalsVisibleTo("VRM10.Tests")]
+[assembly: InternalsVisibleTo("VRM10.Tests.PlayMode")]
+
 namespace UniVRM10
 {
     /// <summary>
     /// Convert vrm0 binary to vrm1 binary. Json processing
     /// </summary>
-    public static class MigrationVrm
+    static internal class MigrationVrm
     {
         public static byte[] Migrate(byte[] src)
         {
diff --git a/Assets/VRM10/Runtime/Migration/MigrationVrmExpression.cs b/Assets/VRM10/Runtime/Migration/MigrationVrmExpression.cs
index 649ebe035..e694a8af8 100644
--- a/Assets/VRM10/Runtime/Migration/MigrationVrmExpression.cs
+++ b/Assets/VRM10/Runtime/Migration/MigrationVrmExpression.cs
@@ -6,7 +6,7 @@ using UnityEngine;
 
 namespace UniVRM10
 {
-    public static class MigrationVrmExpression
+    internal static class MigrationVrmExpression
     {
         /// <summary>
         /// preset 名の文字列から ExpressionPreset を確定させる。