diff --git a/Assets/UniGLTF/Runtime/UniGLTF/IO/TextureIO/GltfTextureImporter.cs b/Assets/UniGLTF/Runtime/UniGLTF/IO/TextureIO/GltfTextureImporter.cs
index 6fdb77787..27cdef130 100644
--- a/Assets/UniGLTF/Runtime/UniGLTF/IO/TextureIO/GltfTextureImporter.cs
+++ b/Assets/UniGLTF/Runtime/UniGLTF/IO/TextureIO/GltfTextureImporter.cs
@@ -12,6 +12,8 @@ namespace UniGLTF
     /// </summary>
     public static class GltfTextureImporter
     {
+        public static bool ImportKhrTextureBasisuExtension { get; set; } = true;
+
         /// <summary>
         /// glTF の Texture が存在せず Image のみのものを、Texture として扱いたい場合の関数.
         /// </summary>
@@ -38,14 +40,15 @@ namespace UniGLTF
         public static bool TryCreateSrgb(GltfData data, int textureIndex, Vector2 offset, Vector2 scale, out SubAssetKey key, out TextureDescriptor desc)
         {
             var gltfTexture = data.GLTF.textures[textureIndex];
-            if (!gltfTexture.source.HasValidIndex())
+            var imageIndex = GetImageIndexFromTextureIndex(data, textureIndex);
+            if (!imageIndex.HasValue)
             {
                 key = default;
                 desc = default;
                 return false;
             }
 
-            var gltfImage = data.GLTF.images[gltfTexture.source.Value];
+            var gltfImage = data.GLTF.images[imageIndex.Value];
             var name = TextureImportName.GetUnityObjectName(TextureImportTypes.sRGB, gltfTexture.name, gltfImage.uri);
             var sampler = TextureSamplerUtil.CreateSampler(data.GLTF, textureIndex);
             desc = new TextureDescriptor(
@@ -55,7 +58,7 @@ namespace UniGLTF
                 TextureImportTypes.sRGB,
                 default,
                 default,
-                () => Task.FromResult(GetImageBytesFromTextureIndex(data, textureIndex)),
+                () => Task.FromResult(GetImageBytesFromImageIndex(data, imageIndex.Value)),
                 default, default, default, default, default);
             key = desc.SubAssetKey;
             return true;
@@ -64,14 +67,15 @@ namespace UniGLTF
         public static bool TryCreateLinear(GltfData data, int textureIndex, Vector2 offset, Vector2 scale, out SubAssetKey key, out TextureDescriptor desc)
         {
             var gltfTexture = data.GLTF.textures[textureIndex];
-            if (!gltfTexture.source.HasValidIndex())
+            var imageIndex = GetImageIndexFromTextureIndex(data, textureIndex);
+            if (!imageIndex.HasValue)
             {
                 key = default;
                 desc = default;
                 return false;
             }
 
-            var gltfImage = data.GLTF.images[gltfTexture.source.Value];
+            var gltfImage = data.GLTF.images[imageIndex.Value];
             var name = TextureImportName.GetUnityObjectName(TextureImportTypes.Linear, gltfTexture.name, gltfImage.uri);
             var sampler = TextureSamplerUtil.CreateSampler(data.GLTF, textureIndex);
             desc = new TextureDescriptor(
@@ -82,7 +86,7 @@ namespace UniGLTF
                 TextureImportTypes.Linear,
                 default,
                 default,
-                () => Task.FromResult(GetImageBytesFromTextureIndex(data, textureIndex)),
+                () => Task.FromResult(GetImageBytesFromImageIndex(data, imageIndex.Value)),
                 default, default, default, default, default);
             key = desc.SubAssetKey;
             return true;
@@ -91,14 +95,15 @@ namespace UniGLTF
         public static bool TryCreateNormal(GltfData data, int textureIndex, Vector2 offset, Vector2 scale, out SubAssetKey key, out TextureDescriptor desc)
         {
             var gltfTexture = data.GLTF.textures[textureIndex];
-            if (!gltfTexture.source.HasValidIndex())
+            var imageIndex = GetImageIndexFromTextureIndex(data, textureIndex);
+            if (!imageIndex.HasValue)
             {
                 key = default;
                 desc = default;
                 return false;
             }
 
-            var gltfImage = data.GLTF.images[gltfTexture.source.Value];
+            var gltfImage = data.GLTF.images[imageIndex.Value];
             var name = TextureImportName.GetUnityObjectName(TextureImportTypes.NormalMap, gltfTexture.name, gltfImage.uri);
             var sampler = TextureSamplerUtil.CreateSampler(data.GLTF, textureIndex);
             desc = new TextureDescriptor(
@@ -109,7 +114,7 @@ namespace UniGLTF
                 TextureImportTypes.NormalMap,
                 default,
                 default,
-                () => Task.FromResult(GetImageBytesFromTextureIndex(data, textureIndex)),
+                () => Task.FromResult(GetImageBytesFromImageIndex(data, imageIndex.Value)),
                 default, default, default, default, default);
             key = desc.SubAssetKey;
             return true;
@@ -118,35 +123,45 @@ namespace UniGLTF
         public static bool TryCreateStandard(GltfData data, int? metallicRoughnessTextureIndex, int? occlusionTextureIndex, Vector2 offset, Vector2 scale, float metallicFactor, float roughnessFactor, out SubAssetKey key, out TextureDescriptor desc)
         {
             string name = default;
-
+            SamplerParam? sampler = default;
             GetTextureBytesAsync getMetallicRoughnessAsync = default;
-            SamplerParam sampler = default;
+            GetTextureBytesAsync getOcclusionAsync = default;
+
             if (metallicRoughnessTextureIndex.HasValue)
             {
                 var gltfTexture = data.GLTF.textures[metallicRoughnessTextureIndex.Value];
-                if (gltfTexture.source.HasValidIndex())
+                var imageIndex = GetImageIndexFromTextureIndex(data, metallicRoughnessTextureIndex.Value);
+                if (imageIndex.HasValue)
                 {
-                    name = TextureImportName.GetUnityObjectName(TextureImportTypes.StandardMap, gltfTexture.name, data.GLTF.images[gltfTexture.source.Value].uri);
+                    var gltfImage = data.GLTF.images[imageIndex.Value];
+                    name = TextureImportName.GetUnityObjectName(TextureImportTypes.StandardMap, gltfTexture.name, gltfImage.uri);
                     sampler = TextureSamplerUtil.CreateSampler(data.GLTF, metallicRoughnessTextureIndex.Value);
-                    getMetallicRoughnessAsync = () => Task.FromResult(GetImageBytesFromTextureIndex(data, metallicRoughnessTextureIndex.Value));
+                    getMetallicRoughnessAsync = () => Task.FromResult(GetImageBytesFromImageIndex(data, imageIndex.Value));
                 }
             }
 
-            GetTextureBytesAsync getOcclusionAsync = default;
             if (occlusionTextureIndex.HasValue)
             {
                 var gltfTexture = data.GLTF.textures[occlusionTextureIndex.Value];
-                if (gltfTexture.source.HasValidIndex())
+                var imageIndex = GetImageIndexFromTextureIndex(data, occlusionTextureIndex.Value);
+                if (imageIndex.HasValue)
                 {
+                    var gltfImage = data.GLTF.images[imageIndex.Value];
                     if (string.IsNullOrEmpty(name))
                     {
-                        name = TextureImportName.GetUnityObjectName(TextureImportTypes.StandardMap, gltfTexture.name, data.GLTF.images[gltfTexture.source.Value].uri);
+                        name = TextureImportName.GetUnityObjectName(TextureImportTypes.StandardMap, gltfTexture.name, gltfImage.uri);
                     }
-                    sampler = TextureSamplerUtil.CreateSampler(data.GLTF, occlusionTextureIndex.Value);
-                    getOcclusionAsync = () => Task.FromResult(GetImageBytesFromTextureIndex(data, occlusionTextureIndex.Value));
+                    sampler ??= TextureSamplerUtil.CreateSampler(data.GLTF, occlusionTextureIndex.Value);
+                    getOcclusionAsync = () => Task.FromResult(GetImageBytesFromImageIndex(data, imageIndex.Value));
                 }
             }
 
+            if (getMetallicRoughnessAsync == null && getOcclusionAsync == null)
+            {
+                key = default;
+                desc = default;
+                return false;
+            }
             if (string.IsNullOrEmpty(name))
             {
                 key = default;
@@ -158,7 +173,7 @@ namespace UniGLTF
                 name,
                 offset,
                 scale,
-                sampler,
+                sampler.Value,
                 TextureImportTypes.StandardMap,
                 metallicFactor,
                 roughnessFactor,
@@ -166,11 +181,6 @@ namespace UniGLTF
                 getOcclusionAsync,
                 default, default, default, default);
             key = desc.SubAssetKey;
-            if (string.IsNullOrEmpty(desc.UnityObjectName))
-            {
-                throw new ArgumentNullException();
-            }
-            Debug.Log("${name}");
             return true;
         }
 
@@ -206,43 +216,47 @@ namespace UniGLTF
             return (offset, scale);
         }
 
-        public static (byte[] binary, string mimeType)? GetImageBytesFromTextureIndex(GltfData data, int textureIndex)
+        private static (byte[] binary, string mimeType)? GetImageBytesFromImageIndex(GltfData data, int imageIndex)
         {
-            if (Application.isPlaying)
+            if (imageIndex >= 0 && imageIndex < data.GLTF.images.Count)
             {
-                // NOTE: Runtime の場合は、拡張を考える.
-                var imageIndex = GetImageIndexFromTexture(data, textureIndex);
-
-                if (textureIndex >= 0 && textureIndex < data.GLTF.textures.Count)
+                var imageBytes = data.GetBytesFromImage(imageIndex);
+                if (imageBytes.HasValue)
                 {
-                    var texture = data.GLTF.textures[textureIndex];
-                    if (glTF_KHR_texture_basisu.TryGet(texture, out var basisuExtension))
+
+                    return (ToArray(imageBytes.Value.binary), imageBytes.Value.mimeType);
+                }
+            }
+
+            return default;
+        }
+
+        private static int? GetImageIndexFromTextureIndex(GltfData data, int textureIndex)
+        {
+            if (textureIndex >= 0 && textureIndex < data.GLTF.textures.Count)
+            {
+                var texture = data.GLTF.textures[textureIndex];
+
+                // NOTE: Runtime の場合は KHR_texture_basisu 拡張を考える.
+                if (ImportKhrTextureBasisuExtension &&
+                    Application.isPlaying &&
+                    glTF_KHR_texture_basisu.TryGet(texture, out var basisuExtension))
+                {
+                    var basisuImageIndex = basisuExtension.source;
+                    if (basisuImageIndex >= 0 && basisuImageIndex < data.GLTF.images.Count)
                     {
-                        imageIndex = basisuExtension.source;
+                        return basisuImageIndex;
                     }
                 }
 
-                if (!imageIndex.HasValue) return default;
-
-                var imageBytes = data.GetBytesFromImage(imageIndex.Value);
-                return (ToArray(imageBytes?.binary ?? default), imageBytes?.mimeType);
+                var imageIndex = texture.source;
+                if (imageIndex >= 0 && imageIndex < data.GLTF.images.Count)
+                {
+                    return imageIndex;
+                }
             }
-            else
-            {
-                // NOTE: Editor の場合は通常通り読み込む.
-                var imageIndex = GetImageIndexFromTexture(data, textureIndex);
-                if (!imageIndex.HasValue) return default;
 
-                var imageBytes = data.GetBytesFromImage(imageIndex.Value);
-                return (ToArray(imageBytes?.binary ?? default), imageBytes?.mimeType);
-            }
-        }
-
-        private static int? GetImageIndexFromTexture(GltfData data, int textureIndex)
-        {
-            if (textureIndex < 0 || textureIndex >= data.GLTF.textures.Count) return default;
-
-            return data.GLTF.textures[textureIndex].source;
+            return default;
         }
 
         private static byte[] ToArray(NativeArray<byte> bytes)
diff --git a/Assets/VRMShaders/GLTF/IO/Runtime/Texture/Importer/TextureDescriptor.cs b/Assets/VRMShaders/GLTF/IO/Runtime/Texture/Importer/TextureDescriptor.cs
index 83c434c58..ac9b01850 100644
--- a/Assets/VRMShaders/GLTF/IO/Runtime/Texture/Importer/TextureDescriptor.cs
+++ b/Assets/VRMShaders/GLTF/IO/Runtime/Texture/Importer/TextureDescriptor.cs
@@ -54,7 +54,7 @@ namespace VRMShaders
         {
             if (string.IsNullOrEmpty(name))
             {
-                throw new ArgumentNullException("name");
+                throw new ArgumentNullException(nameof(name));
             }
             UnityObjectName = name;
             Offset = offset;
diff --git a/Assets/VRM_Samples/SimpleViewer/ViewerUI.cs b/Assets/VRM_Samples/SimpleViewer/ViewerUI.cs
index e73efc003..41dc1ce84 100644
--- a/Assets/VRM_Samples/SimpleViewer/ViewerUI.cs
+++ b/Assets/VRM_Samples/SimpleViewer/ViewerUI.cs
@@ -416,9 +416,10 @@ namespace VRM.SimpleViewer
                 case ".glb":
                 case ".zip":
                     {
-                        var instance = await GltfUtility.LoadBytesAsync(path, bytes,
+                        var instance = await GltfUtility.LoadAsync(path,
                             GetIAwaitCaller(m_useAsync.isOn),
                             GetGltfMaterialGenerator(m_useUrpMaterial.isOn));
+                        SetModel(instance);
                         break;
                     }