diff --git a/android/app/src/main/kotlin/com/example/mini_tias/RawCapturePlugin.kt b/android/app/src/main/kotlin/com/example/mini_tias/RawCapturePlugin.kt
index 017dbc2..a15b6f6 100644
--- a/android/app/src/main/kotlin/com/example/mini_tias/RawCapturePlugin.kt
+++ b/android/app/src/main/kotlin/com/example/mini_tias/RawCapturePlugin.kt
@@ -3,8 +3,11 @@
 import android.app.Activity
 import android.content.Context
 import android.graphics.Bitmap
+import android.graphics.BitmapFactory
 import android.graphics.ImageFormat
 import android.graphics.Matrix
+import android.graphics.Rect
+import android.graphics.YuvImage
 import android.hardware.camera2.*
 import android.media.ImageReader
 import android.media.MediaScannerConnection
@@ -31,6 +34,7 @@
         when (call.method) {
             "captureFullResolutionYuv" -> captureFullResolutionYuv(result)
             "capturePreviewFrame" -> capturePreviewFrame(call, result)
+            "convertYuvToJpeg" -> convertYuvToJpeg(call, result)
             "scanFile" -> {
                 val path = call.argument<String>("path")
                 if (path != null) {
@@ -96,6 +100,67 @@
         }, handler)
     }
 
+    /// YUV_420_888 を NV21 に変換し，YuvImage で JPEG 化して返す．
+    private fun convertYuvToJpeg(call: MethodCall, result: MethodChannel.Result) {
+        try {
+            val width = call.argument<Int>("width")!!
+            val height = call.argument<Int>("height")!!
+            val yPlane = call.argument<ByteArray>("yPlane")!!
+            val uPlane = call.argument<ByteArray>("uPlane")!!
+            val vPlane = call.argument<ByteArray>("vPlane")!!
+            val yRowStride = call.argument<Int>("yRowStride")!!
+            val uvRowStride = call.argument<Int>("uvRowStride")!!
+            val uvPixelStride = call.argument<Int>("uvPixelStride")!!
+            val rotation = call.argument<Int>("rotation") ?: 0
+            val quality = call.argument<Int>("quality") ?: 85
+
+            // YUV_420_888 → NV21 変換
+            val nv21 = ByteArray(width * height * 3 / 2)
+
+            // Y プレーンをコピー
+            for (row in 0 until height) {
+                System.arraycopy(yPlane, row * yRowStride, nv21, row * width, width)
+            }
+
+            // UV プレーンを NV21 形式（VUVU...）にインターリーブ
+            val uvOffset = width * height
+            for (row in 0 until height / 2) {
+                for (col in 0 until width / 2) {
+                    val uvIndex = row * uvRowStride + col * uvPixelStride
+                    nv21[uvOffset + row * width + col * 2] = vPlane[uvIndex]
+                    nv21[uvOffset + row * width + col * 2 + 1] = uPlane[uvIndex]
+                }
+            }
+
+            // NV21 → JPEG
+            val yuvImage = YuvImage(nv21, ImageFormat.NV21, width, height, null)
+            val jpegStream = ByteArrayOutputStream()
+            yuvImage.compressToJpeg(Rect(0, 0, width, height), quality, jpegStream)
+
+            // 回転・反転が必要な場合
+            val mirror = call.argument<Boolean>("mirror") ?: false
+            val jpegBytes = if (rotation != 0 || mirror) {
+                val bitmap = BitmapFactory.decodeByteArray(jpegStream.toByteArray(), 0, jpegStream.size())
+                val matrix = Matrix()
+                if (rotation != 0) matrix.postRotate(rotation.toFloat())
+                if (mirror) matrix.postScale(-1f, 1f)
+                val transformed = Bitmap.createBitmap(bitmap, 0, 0, bitmap.width, bitmap.height, matrix, true)
+                bitmap.recycle()
+
+                val outStream = ByteArrayOutputStream()
+                transformed.compress(Bitmap.CompressFormat.JPEG, quality, outStream)
+                transformed.recycle()
+                outStream.toByteArray()
+            } else {
+                jpegStream.toByteArray()
+            }
+
+            result.success(jpegBytes)
+        } catch (e: Exception) {
+            result.error("CONVERT_ERROR", "YUV to JPEG 変換に失敗: ${e.message}", null)
+        }
+    }
+
     private fun captureFullResolutionYuv(result: MethodChannel.Result) {
         startBackgroundThread()
 
diff --git a/lib/providers/camera_provider.dart b/lib/providers/camera_provider.dart
index 4c5fddb..a24a795 100644
--- a/lib/providers/camera_provider.dart
+++ b/lib/providers/camera_provider.dart
@@ -18,6 +18,8 @@
   bool _permissionPermanentlyDenied = false;
   String? _lastSavedFileName;
   bool _isSaving = false;
+  bool _imageStreamActive = false;
+  Map<String, dynamic>? _latestFrame;
 
   CameraController? get controller => _controller;
   bool get isInitialized => _isInitialized;
@@ -58,6 +60,8 @@
       await _controller!.setFlashMode(FlashMode.off);
       _isInitialized = true;
       _errorMessage = null;
+
+      _startImageStream();
     } catch (e) {
       _errorMessage = 'カメラの初期化に失敗しました: $e';
       _isInitialized = false;
@@ -66,9 +70,61 @@
     notifyListeners();
   }
 
+  /// 画像ストリームを開始して最新フレームを保持する．
+  void _startImageStream() {
+    if (_controller == null || _imageStreamActive) return;
+
+    try {
+      _controller!.startImageStream((CameraImage image) {
+        _latestFrame = {
+          'width': image.width,
+          'height': image.height,
+          'yPlane': Uint8List.fromList(image.planes[0].bytes),
+          'uPlane': Uint8List.fromList(image.planes[1].bytes),
+          'vPlane': Uint8List.fromList(image.planes[2].bytes),
+          'yRowStride': image.planes[0].bytesPerRow,
+          'uvRowStride': image.planes[1].bytesPerRow,
+          'uvPixelStride': image.planes[1].bytesPerPixel ?? 1,
+        };
+      });
+      _imageStreamActive = true;
+    } catch (e) {
+      debugPrint('画像ストリーム開始失敗: $e');
+    }
+  }
+
+  /// 画像ストリームを停止する．
+  Future<void> _stopImageStream() async {
+    if (!_imageStreamActive || _controller == null) return;
+
+    try {
+      await _controller!.stopImageStream();
+    } catch (_) {
+      // 既に停止済みの場合等は無視
+    }
+    _imageStreamActive = false;
+  }
+
+  /// 最新のプレビューフレームを JPEG として取得する（オーバーレイなし）．
+  Future<Uint8List?> capturePreviewSnapshot() async {
+    if (_latestFrame == null) return null;
+
+    final frame = _latestFrame!;
+    return _rawCaptureService.convertYuvToJpeg(
+      width: frame['width'] as int,
+      height: frame['height'] as int,
+      yPlane: frame['yPlane'] as Uint8List,
+      uPlane: frame['uPlane'] as Uint8List,
+      vPlane: frame['vPlane'] as Uint8List,
+      yRowStride: frame['yRowStride'] as int,
+      uvRowStride: frame['uvRowStride'] as int,
+      uvPixelStride: frame['uvPixelStride'] as int,
+      rotation: 90,
+      mirror: true,
+    );
+  }
+
   /// Camera2 API でフル解像度 YUV キャプチャし，PNG で保存する．
-  ///
-  /// プレビューを一時停止 → Camera2 でキャプチャ → プレビュー再開．
   Future<void> takePicture() async {
     if (!_isInitialized || _isSaving) return;
 
@@ -86,7 +142,8 @@
         return;
       }
 
-      // プレビューを停止してカメラを解放
+      // 画像ストリームを停止してカメラを解放
+      await _stopImageStream();
       await _controller?.dispose();
       _controller = null;
 
@@ -118,6 +175,8 @@
 
   /// カメラリソースを解放する．
   void disposeCamera() {
+    _stopImageStream();
+    _latestFrame = null;
     _controller?.dispose();
     _controller = null;
     _isInitialized = false;
diff --git a/lib/screens/capture_screen.dart b/lib/screens/capture_screen.dart
index 26d4f2c..c8a7f14 100644
--- a/lib/screens/capture_screen.dart
+++ b/lib/screens/capture_screen.dart
@@ -5,7 +5,6 @@
 import 'package:provider/provider.dart';
 
 import 'package:mini_tias/providers/camera_provider.dart';
-import 'package:mini_tias/services/raw_capture_service.dart';
 import 'package:mini_tias/widgets/camera_preview.dart';
 import 'package:mini_tias/widgets/shutter_button.dart';
 
@@ -24,8 +23,6 @@
   int? _countdown;
   Timer? _countdownTimer;
   Uint8List? _snapshotBytes;
-  bool _hideOverlay = false;
-  final _rawCaptureService = RawCaptureService();
 
   @override
   void initState() {
@@ -66,39 +63,20 @@
   }
 
   Future<void> _captureWithSnapshot() async {
-    // オーバーレイを非表示にしてからキャプチャ
-    setState(() => _hideOverlay = true);
-    await Future.delayed(const Duration(milliseconds: 50));
+    final cameraProvider = context.read<CameraProvider>();
 
+    // カメラの生フレームからスナップショットを取得（オーバーレイなし，瞬時）
     try {
-      if (!mounted) return;
-      final renderBox = context.findRenderObject() as RenderBox?;
-      if (renderBox != null) {
-        final position = renderBox.localToGlobal(Offset.zero);
-        final size = renderBox.size;
-        final ratio = View.of(context).devicePixelRatio;
-
-        // localToGlobal は回転後の座標（右下）を返すため，左上を計算する
-        final topLeftX = position.dx - size.width;
-        final topLeftY = position.dy - size.height;
-
-        final bytes = await _rawCaptureService.capturePreviewFrame(
-          x: (topLeftX * ratio).round(),
-          y: (topLeftY * ratio).round(),
-          width: (size.width * ratio).round(),
-          height: (size.height * ratio).round(),
-        );
-        setState(() {
-          _snapshotBytes = bytes;
-          _hideOverlay = false;
-        });
+      final bytes = await cameraProvider.capturePreviewSnapshot();
+      if (bytes != null && mounted) {
+        setState(() => _snapshotBytes = bytes);
       }
     } catch (_) {
-      setState(() => _hideOverlay = false);
+      // 失敗しても撮影は続行
     }
 
     if (!mounted) return;
-    context.read<CameraProvider>().takePicture();
+    cameraProvider.takePicture();
   }
 
   void _startCountdown() {
@@ -182,7 +160,7 @@
 
     return Stack(
       children: [
-        // 保存中はスナップショットを表示（Transform なし，Kotlin 側で回転済み）
+        // 保存中はスナップショットを表示
         if (_snapshotBytes != null &&
             (!cameraProvider.isInitialized || cameraProvider.isSaving))
           Positioned.fill(
@@ -237,7 +215,7 @@
             ),
           ),
         // タイマー切り替えボタン（左側）
-        if (!cameraProvider.isSaving && !_hideOverlay)
+        if (!cameraProvider.isSaving)
           Positioned(
             left: 24,
             bottom: 36,
@@ -264,16 +242,14 @@
             ),
           ),
         // シャッターボタン（中央）
-        if (!cameraProvider.isSaving && !_hideOverlay)
+        if (!cameraProvider.isSaving)
           Positioned(
             left: 0,
             right: 0,
             bottom: 24,
             child: Center(
               child: ShutterButton(
-                onPressed: cameraProvider.isSaving || _countdown != null
-                    ? () {}
-                    : _onShutterPressed,
+                onPressed: _countdown != null ? () {} : _onShutterPressed,
               ),
             ),
           ),
diff --git a/lib/services/file_service.dart b/lib/services/file_service.dart
index dce0606..e169f32 100644
--- a/lib/services/file_service.dart
+++ b/lib/services/file_service.dart
@@ -143,6 +143,9 @@
       }
     }
 
-    return Uint8List.fromList(img.encodePng(image));
+    // センサーの向き（270°）を補正するため 90° 時計回りに回転
+    final rotated = img.copyRotate(image, angle: 90);
+
+    return Uint8List.fromList(img.encodePng(rotated));
   }
 }
diff --git a/lib/services/raw_capture_service.dart b/lib/services/raw_capture_service.dart
index 96faec2..35eebb5 100644
--- a/lib/services/raw_capture_service.dart
+++ b/lib/services/raw_capture_service.dart
@@ -32,6 +32,39 @@
     return result;
   }
 
+  /// YUV_420_888 を JPEG に変換する（Android ネイティブの高速変換）．
+  Future<Uint8List> convertYuvToJpeg({
+    required int width,
+    required int height,
+    required Uint8List yPlane,
+    required Uint8List uPlane,
+    required Uint8List vPlane,
+    required int yRowStride,
+    required int uvRowStride,
+    required int uvPixelStride,
+    int rotation = 0,
+    bool mirror = false,
+    int quality = 85,
+  }) async {
+    final result = await _channel.invokeMethod<Uint8List>('convertYuvToJpeg', {
+      'width': width,
+      'height': height,
+      'yPlane': yPlane,
+      'uPlane': uPlane,
+      'vPlane': vPlane,
+      'yRowStride': yRowStride,
+      'uvRowStride': uvRowStride,
+      'uvPixelStride': uvPixelStride,
+      'rotation': rotation,
+      'mirror': mirror,
+      'quality': quality,
+    });
+    if (result == null) {
+      throw Exception('YUV to JPEG 変換に失敗しました');
+    }
+    return result;
+  }
+
   /// MediaStore にファイルを登録し，PC から MTP で見えるようにする．
   Future<void> scanFile(String path) async {
     await _channel.invokeMethod('scanFile', {'path': path});