diff --git a/Assets/VRM/Runtime/Format/VRMFormat.cs b/Assets/VRM/Runtime/Format/glTF_VRM_extensions.cs
similarity index 61%
rename from Assets/VRM/Runtime/Format/VRMFormat.cs
rename to Assets/VRM/Runtime/Format/glTF_VRM_extensions.cs
index 548ab400c..26340156d 100644
--- a/Assets/VRM/Runtime/Format/VRMFormat.cs
+++ b/Assets/VRM/Runtime/Format/glTF_VRM_extensions.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Collections.Generic;
 using UniGLTF;
-
+using UniJSON;
 
 namespace VRM
 {
@@ -11,13 +11,9 @@ VRM extension is for 3d humanoid avatars (and models) in VR applications.
 ")]
     public class glTF_VRM_extensions
     {
-        public static string ExtensionName
-        {
-            get
-            {
-                return "VRM";
-            }
-        }
+        public const string ExtensionName = "VRM";
+
+        public static readonly Utf8String ExtensionNameUtf8 = Utf8String.From(ExtensionName);
 
         [JsonSchema(Description = @"Version of exporter that vrm created. " + VRMVersion.VRM_VERSION)]
         public string exporterVersion = "UniVRM-" + VRMVersion.VERSION;
@@ -31,5 +27,23 @@ VRM extension is for 3d humanoid avatars (and models) in VR applications.
         public glTF_VRM_BlendShapeMaster blendShapeMaster = new glTF_VRM_BlendShapeMaster();
         public glTF_VRM_SecondaryAnimation secondaryAnimation = new glTF_VRM_SecondaryAnimation();
         public List<glTF_VRM_Material> materialProperties = new List<glTF_VRM_Material>();
+
+        public static bool TryDeserilize(glTFExtension extension, out glTF_VRM_extensions vrm)
+        {            
+            if (extension is glTFExtensionImport import)
+            {
+                foreach (var kv in import.ObjectItems())
+                {
+                    if (kv.Key.GetUtf8String() == ExtensionNameUtf8)
+                    {
+                        vrm = VrmDeserializer.Deserialize(kv.Value);
+                        return true;
+                    }
+                }
+            }
+
+            vrm = default;
+            return false;
+        }
     }
 }
diff --git a/Assets/VRM/Runtime/Format/VRMFormat.cs.meta b/Assets/VRM/Runtime/Format/glTF_VRM_extensions.cs.meta
similarity index 71%
rename from Assets/VRM/Runtime/Format/VRMFormat.cs.meta
rename to Assets/VRM/Runtime/Format/glTF_VRM_extensions.cs.meta
index ae2eaf1f5..5cf92e8ef 100644
--- a/Assets/VRM/Runtime/Format/VRMFormat.cs.meta
+++ b/Assets/VRM/Runtime/Format/glTF_VRM_extensions.cs.meta
@@ -1,7 +1,5 @@
 fileFormatVersion: 2
-guid: 20eca00211c61d047b586f852b818b8f
-timeCreated: 1517308526
-licenseType: Free
+guid: d58b001b3cfa63e41b4d2d6afa403f5d
 MonoImporter:
   externalObjects: {}
   serializedVersion: 2
diff --git a/Assets/VRM/Runtime/IO/VRMImporterContext.cs b/Assets/VRM/Runtime/IO/VRMImporterContext.cs
index 96a8ee827..9921b6ba2 100644
--- a/Assets/VRM/Runtime/IO/VRMImporterContext.cs
+++ b/Assets/VRM/Runtime/IO/VRMImporterContext.cs
@@ -38,18 +38,12 @@ namespace VRM
             base.ParseJson(json, storage);
 
             // parse VRM part
-            if (GLTF.extensions is glTFExtensionImport imported)
+            if (glTF_VRM_extensions.TryDeserilize(GLTF.extensions, out glTF_VRM_extensions vrm))
             {
-                foreach (var kv in imported.ObjectItems())
-                {
-                    if (kv.Key.GetString() == "VRM")
-                    {
-                        VRM = VrmDeserializer.Deserialize(kv.Value);
-                        break;
-                    }
-                }
+                VRM = vrm;
             }
 
+            // override material importer
             SetMaterialImporter(new VRMMaterialImporter(this, VRM.materialProperties));
         }