diff --git a/tools/merge_engine_manifest.py b/tools/merge_engine_manifest.py
new file mode 100644
index 000000000..d90f846d8
--- /dev/null
+++ b/tools/merge_engine_manifest.py
@@ -0,0 +1,49 @@
+"""
+エンジンマニフェストをマージする。
+"""
+
+import argparse
+import json
+from pathlib import Path
+
+JsonValue = str | int | float
+
+
+def merge_json_string(src: str, dst: str) -> str:
+    src_json: dict[str, JsonValue | dict[str, dict]] = json.loads(src)
+    dst_json: dict[str, JsonValue | dict[str, dict]] = json.loads(dst)
+
+    for key, dst_value in dst_json.items():
+        assert key in src_json, f"Key {key} is not found in src_json"
+
+        # `manage_library` のみdictなので特別に処理
+        if key == "supported_features":
+            assert isinstance(dst_value, dict)
+
+            src_value = src_json[key]
+            assert isinstance(src_value, dict)
+            src_value.update(dst_value)
+
+        else:
+            src_value = src_json[key]
+            assert isinstance(src_value, JsonValue)
+            assert isinstance(dst_value, JsonValue)
+            src_json[key] = dst_value
+
+    return json.dumps(src_json, ensure_ascii=False)
+
+
+def merge_engine_manifest(src_path: Path, dst_path: Path, output_path: Path) -> None:
+    src = src_path.read_text(encoding="utf-8")
+    dst = dst_path.read_text(encoding="utf-8")
+    merged = merge_json_string(src, dst)
+    output_path.write_text(merged, encoding="utf-8")
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument("src_path", type=Path)
+    parser.add_argument("dst_path", type=Path)
+    parser.add_argument("output_path", type=Path)
+    args = parser.parse_args()
+    merge_engine_manifest(args.src_path, args.dst_path, args.output_path)
diff --git a/tools/merge_update_infos.py b/tools/merge_update_infos.py
index 7c1ea5784..8ae08cb27 100644
--- a/tools/merge_update_infos.py
+++ b/tools/merge_update_infos.py
@@ -42,14 +42,14 @@ def merge_json_string(src: str, dst: str) -> str:
                     # 異なるものがあった場合だけ後ろに付け足す
                     src_item[key] = list(OrderedDict.fromkeys(src_value + dst_value))
 
-    return json.dumps(src_json)
+    return json.dumps(src_json, ensure_ascii=False)
 
 
 def merge_update_infos(src_path: Path, dst_path: Path, output_path: Path) -> None:
     src = src_path.read_text(encoding="utf-8")
     dst = dst_path.read_text(encoding="utf-8")
     merged = merge_json_string(src, dst)
-    output_path.write_text(merged)
+    output_path.write_text(merged, encoding="utf-8")
 
 
 if __name__ == "__main__":
diff --git a/tools/process_voicevox_resource.bash b/tools/process_voicevox_resource.bash
index 086557209..acdc32ae8 100644
--- a/tools/process_voicevox_resource.bash
+++ b/tools/process_voicevox_resource.bash
@@ -13,10 +13,11 @@ cp -r "${DOWNLOAD_RESOURCE_PATH}/character_info" resources/character_info
 python "${DOWNLOAD_RESOURCE_PATH}/scripts/clean_character_info.py" \
     --character_info_dir resources/character_info/
 
-# エンジンマニフェストに含まれるダミーの情報を上書きする
-jq -s '.[0] * .[1]' engine_manifest.json "${DOWNLOAD_RESOURCE_PATH}/engine/engine_manifest.json" \
-    > engine_manifest.json.tmp
-mv engine_manifest.json.tmp engine_manifest.json
+# エンジンマニフェストを統合する
+python tools/merge_engine_manifest.py \
+    engine_manifest.json \
+    "${DOWNLOAD_RESOURCE_PATH}/engine/engine_manifest.json" \
+    engine_manifest.json
 
 # エンジンとリソースの更新情報を統合する
 python tools/merge_update_infos.py \