diff --git a/run.py b/run.py
index ab4a0d09f..92a70d0ce 100644
--- a/run.py
+++ b/run.py
@@ -13,7 +13,7 @@
 from io import BytesIO, TextIOWrapper
 from pathlib import Path
 from tempfile import NamedTemporaryFile, TemporaryFile
-from typing import Annotated, Literal, Optional
+from typing import Annotated, Any, Literal, Optional
 
 import soundfile
 import uvicorn
@@ -211,7 +211,7 @@ async def block_origin_middleware(
             )
 
     # 許可されていないAPIを無効化する
-    def check_disabled_mutable_api():
+    def check_disabled_mutable_api() -> None:
         if disable_mutable_api:
             raise HTTPException(
                 status_code=403,
@@ -249,7 +249,7 @@ def check_disabled_mutable_api():
     #         _ = loop.create_task(cancellable_engine.catch_disconnection())
 
     @app.on_event("startup")
-    def apply_user_dict():
+    def apply_user_dict() -> None:
         update_dict()
 
     def get_engine(core_version: Optional[str]) -> TTSEngine:
@@ -1389,7 +1389,7 @@ def setting_post(
 
     # BaseLibraryInfo/VvlibManifestモデルはAPIとして表には出ないが、エディタ側で利用したいので、手動で追加する
     # ref: https://fastapi.tiangolo.com/advanced/extending-openapi/#modify-the-openapi-schema
-    def custom_openapi():
+    def custom_openapi() -> Any:
         if app.openapi_schema:
             return app.openapi_schema
         openapi_schema = get_openapi(
diff --git a/test/e2e/conftest.py b/test/e2e/conftest.py
index df5bb1744..61e6b9315 100644
--- a/test/e2e/conftest.py
+++ b/test/e2e/conftest.py
@@ -1,4 +1,5 @@
 from pathlib import Path
+from typing import Any
 
 import pytest
 from fastapi import FastAPI
@@ -13,7 +14,7 @@
 
 
 @pytest.fixture(scope="session")
-def app_params():
+def app_params() -> dict[str, Any]:
     cores = initialize_cores(use_gpu=False, enable_mock=True)
     tts_engines = make_tts_engines_from_cores(cores)
     latest_core_version = get_latest_core_version(versions=list(tts_engines.keys()))
diff --git a/test/preset/test_preset.py b/test/preset/test_preset.py
index 1cd871a93..4a3b61609 100644
--- a/test/preset/test_preset.py
+++ b/test/preset/test_preset.py
@@ -15,52 +15,52 @@
 
 
 class TestPresetManager(TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         self.tmp_dir = TemporaryDirectory()
         self.tmp_dir_path = Path(self.tmp_dir.name)
 
-    def tearDown(self):
+    def tearDown(self) -> None:
         self.tmp_dir.cleanup()
 
-    def test_validation(self):
+    def test_validation(self) -> None:
         preset_manager = PresetManager(preset_path=presets_test_1_yaml_path)
         presets = preset_manager.load_presets()
         self.assertFalse(presets is None)
 
-    def test_validation_same(self):
+    def test_validation_same(self) -> None:
         preset_manager = PresetManager(preset_path=presets_test_1_yaml_path)
         presets = preset_manager.load_presets()
         presets2 = preset_manager.load_presets()
         self.assertFalse(presets is None)
         self.assertEqual(presets, presets2)
 
-    def test_validation_2(self):
+    def test_validation_2(self) -> None:
         preset_manager = PresetManager(preset_path=presets_test_2_yaml_path)
         with self.assertRaises(
             PresetError, msg="プリセットの設定ファイルにミスがあります"
         ):
             preset_manager.load_presets()
 
-    def test_preset_id(self):
+    def test_preset_id(self) -> None:
         preset_manager = PresetManager(preset_path=presets_test_3_yaml_path)
         with self.assertRaises(PresetError, msg="プリセットのidに重複があります"):
             preset_manager.load_presets()
 
-    def test_empty_file(self):
+    def test_empty_file(self) -> None:
         preset_manager = PresetManager(preset_path=presets_test_4_yaml_path)
         with self.assertRaises(
             PresetError, msg="プリセットの設定ファイルが空の内容です"
         ):
             preset_manager.load_presets()
 
-    def test_not_exist_file(self):
+    def test_not_exist_file(self) -> None:
         preset_manager = PresetManager(preset_path=Path("test/presets-dummy.yaml"))
         with self.assertRaises(
             PresetError, msg="プリセットの設定ファイルが見つかりません"
         ):
             preset_manager.load_presets()
 
-    def test_add_preset(self):
+    def test_add_preset(self) -> None:
         temp_path = self.tmp_dir_path / "presets-test-temp.yaml"
         copyfile(presets_test_1_yaml_path, temp_path)
         preset_manager = PresetManager(preset_path=temp_path)
@@ -86,7 +86,7 @@ def test_add_preset(self):
                 self.assertEqual(_preset, preset)
         remove(temp_path)
 
-    def test_add_preset_load_failure(self):
+    def test_add_preset_load_failure(self) -> None:
         preset_manager = PresetManager(preset_path=presets_test_2_yaml_path)
         with self.assertRaises(
             PresetError, msg="プリセットの設定ファイルにミスがあります"
@@ -108,7 +108,7 @@ def test_add_preset_load_failure(self):
                 )
             )
 
-    def test_add_preset_conflict_id(self):
+    def test_add_preset_conflict_id(self) -> None:
         temp_path = self.tmp_dir_path / "presets-test-temp.yaml"
         copyfile(presets_test_1_yaml_path, temp_path)
         preset_manager = PresetManager(preset_path=temp_path)
@@ -134,7 +134,7 @@ def test_add_preset_conflict_id(self):
                 self.assertEqual(_preset, preset)
         remove(temp_path)
 
-    def test_add_preset_conflict_id2(self):
+    def test_add_preset_conflict_id2(self) -> None:
         temp_path = self.tmp_dir_path / "presets-test-temp.yaml"
         copyfile(presets_test_1_yaml_path, temp_path)
         preset_manager = PresetManager(preset_path=temp_path)
@@ -160,7 +160,7 @@ def test_add_preset_conflict_id2(self):
                 self.assertEqual(_preset, preset)
         remove(temp_path)
 
-    def test_add_preset_write_failure(self):
+    def test_add_preset_write_failure(self) -> None:
         temp_path = self.tmp_dir_path / "presets-test-temp.yaml"
         copyfile(presets_test_1_yaml_path, temp_path)
         preset_manager = PresetManager(preset_path=temp_path)
@@ -188,7 +188,7 @@ def test_add_preset_write_failure(self):
         self.assertEqual(len(preset_manager.presets), 2)
         remove(temp_path)
 
-    def test_update_preset(self):
+    def test_update_preset(self) -> None:
         temp_path = self.tmp_dir_path / "presets-test-temp.yaml"
         copyfile(presets_test_1_yaml_path, temp_path)
         preset_manager = PresetManager(preset_path=temp_path)
@@ -214,7 +214,7 @@ def test_update_preset(self):
                 self.assertEqual(_preset, preset)
         remove(temp_path)
 
-    def test_update_preset_load_failure(self):
+    def test_update_preset_load_failure(self) -> None:
         preset_manager = PresetManager(preset_path=presets_test_2_yaml_path)
         with self.assertRaises(
             PresetError, msg="プリセットの設定ファイルにミスがあります"
@@ -236,7 +236,7 @@ def test_update_preset_load_failure(self):
                 )
             )
 
-    def test_update_preset_not_found(self):
+    def test_update_preset_not_found(self) -> None:
         temp_path = self.tmp_dir_path / "presets-test-temp.yaml"
         copyfile(presets_test_1_yaml_path, temp_path)
         preset_manager = PresetManager(preset_path=temp_path)
@@ -259,7 +259,7 @@ def test_update_preset_not_found(self):
         self.assertEqual(len(preset_manager.presets), 2)
         remove(temp_path)
 
-    def test_update_preset_write_failure(self):
+    def test_update_preset_write_failure(self) -> None:
         temp_path = self.tmp_dir_path / "presets-test-temp.yaml"
         copyfile(presets_test_1_yaml_path, temp_path)
         preset_manager = PresetManager(preset_path=temp_path)
@@ -288,7 +288,7 @@ def test_update_preset_write_failure(self):
         self.assertEqual(preset_manager.presets[0].name, "test")
         remove(temp_path)
 
-    def test_delete_preset(self):
+    def test_delete_preset(self) -> None:
         temp_path = self.tmp_dir_path / "presets-test-temp.yaml"
         copyfile(presets_test_1_yaml_path, temp_path)
         preset_manager = PresetManager(preset_path=temp_path)
@@ -297,14 +297,14 @@ def test_delete_preset(self):
         self.assertEqual(len(preset_manager.presets), 1)
         remove(temp_path)
 
-    def test_delete_preset_load_failure(self):
+    def test_delete_preset_load_failure(self) -> None:
         preset_manager = PresetManager(preset_path=presets_test_2_yaml_path)
         with self.assertRaises(
             PresetError, msg="プリセットの設定ファイルにミスがあります"
         ):
             preset_manager.delete_preset(10)
 
-    def test_delete_preset_not_found(self):
+    def test_delete_preset_not_found(self) -> None:
         temp_path = self.tmp_dir_path / "presets-test-temp.yaml"
         copyfile(presets_test_1_yaml_path, temp_path)
         preset_manager = PresetManager(preset_path=temp_path)
@@ -313,7 +313,7 @@ def test_delete_preset_not_found(self):
         self.assertEqual(len(preset_manager.presets), 2)
         remove(temp_path)
 
-    def test_delete_preset_write_failure(self):
+    def test_delete_preset_write_failure(self) -> None:
         temp_path = self.tmp_dir_path / "presets-test-temp.yaml"
         copyfile(presets_test_1_yaml_path, temp_path)
         preset_manager = PresetManager(preset_path=temp_path)
diff --git a/test/setting/test_setting.py b/test/setting/test_setting.py
index 468e76b11..6b4d63d4c 100644
--- a/test/setting/test_setting.py
+++ b/test/setting/test_setting.py
@@ -7,11 +7,11 @@
 
 
 class TestSettingLoader(TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         self.tmp_dir = TemporaryDirectory()
         self.tmp_dir_path = Path(self.tmp_dir.name)
 
-    def test_loading_1(self):
+    def test_loading_1(self) -> None:
         setting_loader = SettingHandler(Path("not_exist.yaml"))
         settings = setting_loader.load()
 
@@ -20,7 +20,7 @@ def test_loading_1(self):
             {"allow_origin": None, "cors_policy_mode": CorsPolicyMode.localapps},
         )
 
-    def test_loading_2(self):
+    def test_loading_2(self) -> None:
         setting_loader = SettingHandler(
             setting_file_path=Path("test/setting/setting-test-load-1.yaml")
         )
@@ -31,7 +31,7 @@ def test_loading_2(self):
             {"allow_origin": None, "cors_policy_mode": CorsPolicyMode.localapps},
         )
 
-    def test_loading_3(self):
+    def test_loading_3(self) -> None:
         setting_loader = SettingHandler(
             setting_file_path=Path("test/setting/setting-test-load-2.yaml")
         )
@@ -42,7 +42,7 @@ def test_loading_3(self):
             {"allow_origin": None, "cors_policy_mode": "all"},
         )
 
-    def test_loading_4(self):
+    def test_loading_4(self) -> None:
         setting_loader = SettingHandler(
             setting_file_path=Path("test/setting/setting-test-load-3.yaml")
         )
@@ -56,7 +56,7 @@ def test_loading_4(self):
             },
         )
 
-    def test_dump(self):
+    def test_dump(self) -> None:
         setting_loader = SettingHandler(
             setting_file_path=Path(self.tmp_dir_path / "setting-test-dump.yaml")
         )
@@ -69,5 +69,5 @@ def test_dump(self):
             {"allow_origin": None, "cors_policy_mode": CorsPolicyMode.localapps},
         )
 
-    def tearDown(self):
+    def tearDown(self) -> None:
         self.tmp_dir.cleanup()
diff --git a/test/test_connect_base64_waves.py b/test/test_connect_base64_waves.py
index 96cf92d1b..2bdc54abb 100644
--- a/test/test_connect_base64_waves.py
+++ b/test/test_connect_base64_waves.py
@@ -55,7 +55,7 @@ def generate_sine_wave_base64(seconds: float, samplerate: int, frequency: float)
 
 
 class TestConnectBase64Waves(TestCase):
-    def test_connect(self):
+    def test_connect(self) -> None:
         samplerate = 1000
         wave = generate_sine_wave_ndarray(
             seconds=2, samplerate=samplerate, frequency=10
@@ -70,10 +70,10 @@ def test_connect(self):
 
         self.assertTrue((wave_x2_ref == wave_x2).all())
 
-    def test_no_wave_error(self):
+    def test_no_wave_error(self) -> None:
         self.assertRaises(ConnectBase64WavesException, connect_base64_waves, waves=[])
 
-    def test_invalid_base64_error(self):
+    def test_invalid_base64_error(self) -> None:
         wave_1000hz = generate_sine_wave_base64(
             seconds=2, samplerate=1000, frequency=10
         )
@@ -87,7 +87,7 @@ def test_invalid_base64_error(self):
             ],
         )
 
-    def test_invalid_wave_file_error(self):
+    def test_invalid_wave_file_error(self) -> None:
         wave_1000hz = generate_sine_wave_bytes(seconds=2, samplerate=1000, frequency=10)
         wave_1000hz_broken_bytes = wave_1000hz[1:]  # remove head 1 byte
         wave_1000hz_broken = encode_base64(wave_1000hz_broken_bytes)
@@ -100,7 +100,7 @@ def test_invalid_wave_file_error(self):
             ],
         )
 
-    def test_different_frequency(self):
+    def test_different_frequency(self) -> None:
         wave_24000hz = generate_sine_wave_ndarray(
             seconds=1, samplerate=24000, frequency=10
         )
@@ -118,7 +118,7 @@ def test_different_frequency(self):
         self.assertEqual(wave_x2_ref.shape, wave_x2.shape)
         numpy.testing.assert_array_almost_equal(wave_x2_ref, wave_x2)
 
-    def test_different_channels(self):
+    def test_different_channels(self) -> None:
         wave_1000hz = generate_sine_wave_ndarray(
             seconds=2, samplerate=1000, frequency=10
         )
diff --git a/test/test_core_version_utility.py b/test/test_core_version_utility.py
index 7ac191011..bff4b19a2 100644
--- a/test/test_core_version_utility.py
+++ b/test/test_core_version_utility.py
@@ -7,7 +7,7 @@
 
 
 class TestCoreVersion(TestCase):
-    def test_parse_core_version(self):
+    def test_parse_core_version(self) -> None:
         parse_core_version("0.0.0")
         parse_core_version("0.1.0")
         parse_core_version("0.10.0")
@@ -16,7 +16,7 @@ def test_parse_core_version(self):
         parse_core_version("0.14.0-preview.1")
         parse_core_version("0.14.0-preview.10")
 
-    def test_get_latest_core_version(self):
+    def test_get_latest_core_version(self) -> None:
         self.assertEqual(
             get_latest_core_version(
                 versions=[
diff --git a/test/test_library_manager.py b/test/test_library_manager.py
index 521311694..020a5111e 100644
--- a/test/test_library_manager.py
+++ b/test/test_library_manager.py
@@ -16,7 +16,7 @@
 
 
 class TestLibraryManager(TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         super().setUp()
         self.tmp_dir = TemporaryDirectory()
         self.tmp_dir_path = Path(self.tmp_dir.name)
@@ -39,7 +39,7 @@ def setUp(self):
             zf.writestr(vvlib_manifest_name, json.dumps(self.vvlib_manifest))
         self.library_file = open(self.library_filename, "br")
 
-    def tearDown(self):
+    def tearDown(self) -> None:
         self.tmp_dir.cleanup()
         self.library_file.close()
         self.library_filename.unlink()
@@ -58,7 +58,7 @@ def create_vvlib_manifest(self, **kwargs):
         vvlib_manifest = copy.deepcopy(self.vvlib_manifest)
         return {**vvlib_manifest, **kwargs}
 
-    def test_installed_libraries(self):
+    def test_installed_libraries(self) -> None:
         self.assertEqual(self.library_manger.installed_libraries(), {})
 
         self.library_manger.install_library(
@@ -73,7 +73,7 @@ def test_installed_libraries(self):
         self.library_manger.uninstall_library(self.library_uuid)
         self.assertEqual(self.library_manger.installed_libraries(), {})
 
-    def test_install_library(self):
+    def test_install_library(self) -> None:
         # エンジンが把握していないライブラリのテスト
         invalid_uuid = "52398bd5-3cc3-406c-a159-dfec5ace4bab"
         with self.assertRaises(HTTPException) as e:
@@ -193,7 +193,7 @@ def test_install_library(self):
 
         os.remove(invalid_vvlib_name)
 
-    def test_uninstall_library(self):
+    def test_uninstall_library(self) -> None:
         # TODO: アンインストール出来ないライブラリをテストできるようにしたい
         with self.assertRaises(HTTPException) as e:
             self.library_manger.uninstall_library(self.library_uuid)
diff --git a/test/test_metas_store.py b/test/test_metas_store.py
index cf354928a..42d8cf35d 100644
--- a/test/test_metas_store.py
+++ b/test/test_metas_store.py
@@ -30,7 +30,7 @@ def _equal_speakers(a: list[Speaker], b: list[Speaker]) -> bool:
 
 
 class TestMetasStore(TestCase):
-    def test_filter_speakers_and_styles_with_speaker(self):
+    def test_filter_speakers_and_styles_with_speaker(self) -> None:
         # Inputs
         speaker_talk_only = _gen_speaker(["talk"])
         speaker_singing_teacher_only = _gen_speaker(["singing_teacher"])
@@ -63,7 +63,7 @@ def test_filter_speakers_and_styles_with_speaker(self):
             for style in speaker.styles:
                 self.assertEqual(style.type, "talk")
 
-    def test_filter_speakers_and_styles_with_singer(self):
+    def test_filter_speakers_and_styles_with_singer(self) -> None:
         # Inputs
         speaker_talk_only = _gen_speaker(["talk"])
         speaker_singing_teacher_only = _gen_speaker(["singing_teacher"])
diff --git a/test/test_mock_tts_engine.py b/test/test_mock_tts_engine.py
index ef6bea1d5..eaeda7990 100644
--- a/test/test_mock_tts_engine.py
+++ b/test/test_mock_tts_engine.py
@@ -19,7 +19,7 @@ def _gen_mora(text: str, consonant: str | None, vowel: str) -> Mora:
 
 
 class TestMockTTSEngine(TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         super().setUp()
 
         self.accent_phrases_hello_hiho = [
@@ -47,15 +47,15 @@ def setUp(self):
         ]
         self.engine = MockTTSEngine()
 
-    def test_update_length(self):
+    def test_update_length(self) -> None:
         """`.update_length()` がエラー無く生成をおこなう"""
         self.engine.update_length(self.accent_phrases_hello_hiho, StyleId(0))
 
-    def test_update_pitch(self):
+    def test_update_pitch(self) -> None:
         """`.update_pitch()` がエラー無く生成をおこなう"""
         self.engine.update_pitch(self.accent_phrases_hello_hiho, StyleId(0))
 
-    def test_synthesize_wave(self):
+    def test_synthesize_wave(self) -> None:
         """`.synthesize_wave()` がエラー無く生成をおこなう"""
         self.engine.synthesize_wave(
             AudioQuery(
diff --git a/test/tts_pipeline/test_kana_converter.py b/test/tts_pipeline/test_kana_converter.py
index f5e20ff39..f16f87be2 100644
--- a/test/tts_pipeline/test_kana_converter.py
+++ b/test/tts_pipeline/test_kana_converter.py
@@ -11,7 +11,7 @@ def parse_kana(text: str) -> list[AccentPhrase]:
 
 
 class TestParseKana(TestCase):
-    def test_phrase_length(self):
+    def test_phrase_length(self) -> None:
         self.assertEqual(len(parse_kana("ア'/ア'")), 2)
         self.assertEqual(len(parse_kana("ア'、ア'")), 2)
         self.assertEqual(len(parse_kana("ア'/ア'/ア'/ア'/ア'")), 5)
@@ -20,7 +20,7 @@ def test_phrase_length(self):
         self.assertEqual(len(parse_kana("ギェ'")), 1)
         self.assertEqual(len(parse_kana("ギェ'、ギェ'/ギェ'")), 3)
 
-    def test_accent(self):
+    def test_accent(self) -> None:
         self.assertEqual(parse_kana("シャ'シシュシェショ")[0].accent, 1)
         self.assertEqual(parse_kana("シャ'_シシュシェショ")[0].accent, 1)
         self.assertEqual(parse_kana("シャシ'シュシェショ")[0].accent, 2)
@@ -30,7 +30,7 @@ def test_accent(self):
         self.assertEqual(parse_kana("シャシシュシェショ'")[0].accent, 5)
         self.assertEqual(parse_kana("シャ_シシュシェショ'")[0].accent, 5)
 
-    def test_mora_length(self):
+    def test_mora_length(self) -> None:
         self.assertEqual(len(parse_kana("シャ'シシュシェショ")[0].moras), 5)
         self.assertEqual(len(parse_kana("シャ'_シシュシェショ")[0].moras), 5)
         self.assertEqual(len(parse_kana("シャシ'シュシェショ")[0].moras), 5)
@@ -38,17 +38,17 @@ def test_mora_length(self):
         self.assertEqual(len(parse_kana("シャシシュシェショ'")[0].moras), 5)
         self.assertEqual(len(parse_kana("シャ_シシュシェショ'")[0].moras), 5)
 
-    def test_pause(self):
+    def test_pause(self) -> None:
         self.assertIsNone(parse_kana("ア'/ア'")[0].pause_mora)
         self.assertIsNone(parse_kana("ア'/ア'")[1].pause_mora)
         self.assertIsNotNone(parse_kana("ア'、ア'")[0].pause_mora)
         self.assertIsNone(parse_kana("ア'、ア'")[1].pause_mora)
 
-    def test_unvoice(self):
+    def test_unvoice(self) -> None:
         self.assertEqual(parse_kana("ス'")[0].moras[0].vowel, "u")
         self.assertEqual(parse_kana("_ス'")[0].moras[0].vowel, "U")
 
-    def test_roundtrip(self):
+    def test_roundtrip(self) -> None:
         for text in [
             "コンニチワ'",
             "ワタシワ'/シャチョオデ'_ス",
@@ -65,8 +65,8 @@ def _accent_phrase_marks_base(
         accent_phrases = kana_converter.parse_kana(text)
         self.assertEqual(expected_accent_phrases, accent_phrases)
 
-    def test_accent_phrase_marks(self):
-        def a_slash_a_accent_phrases():
+    def test_accent_phrase_marks(self) -> None:
+        def a_slash_a_accent_phrases() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
@@ -104,7 +104,7 @@ def a_slash_a_accent_phrases():
             expected_accent_phrases=expected_accent_phrases,
         )
 
-        def a_jp_comma_a_accent_phrases():
+        def a_jp_comma_a_accent_phrases() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
@@ -149,7 +149,7 @@ def a_jp_comma_a_accent_phrases():
             expected_accent_phrases=expected_accent_phrases,
         )
 
-        def a_slash_a_slash_a_slash_a_slash_a_accent_phrases():
+        def a_slash_a_slash_a_slash_a_slash_a_accent_phrases() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
@@ -229,7 +229,7 @@ def a_slash_a_slash_a_slash_a_slash_a_accent_phrases():
             expected_accent_phrases=expected_accent_phrases,
         )
 
-        def su_accent_phrases():
+        def su_accent_phrases() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
@@ -253,7 +253,7 @@ def su_accent_phrases():
             expected_accent_phrases=expected_accent_phrases,
         )
 
-        def under_score_su_accent_phrases():
+        def under_score_su_accent_phrases() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
@@ -277,7 +277,7 @@ def under_score_su_accent_phrases():
             expected_accent_phrases=expected_accent_phrases,
         )
 
-        def gye_accent_phrases():
+        def gye_accent_phrases() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
@@ -301,7 +301,7 @@ def gye_accent_phrases():
             expected_accent_phrases=expected_accent_phrases,
         )
 
-        def gye_gye_gye_accent_phrases():
+        def gye_gye_gye_accent_phrases() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
@@ -360,8 +360,8 @@ def gye_gye_gye_accent_phrases():
             expected_accent_phrases=expected_accent_phrases,
         )
 
-    def test_interrogative_accent_phrase_marks(self):
-        def a_question_mark_accent_phrases():
+    def test_interrogative_accent_phrase_marks(self) -> None:
+        def a_question_mark_accent_phrases() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
@@ -386,7 +386,7 @@ def a_question_mark_accent_phrases():
             expected_accent_phrases=expected_accent_phrases,
         )
 
-        def gye_gye_gye_question_mark_accent_phrases():
+        def gye_gye_gye_question_mark_accent_phrases() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
@@ -446,7 +446,9 @@ def gye_gye_gye_question_mark_accent_phrases():
             expected_accent_phrases=expected_accent_phrases,
         )
 
-        def a_pause_a_question_pause_a_question_a_question_mark_accent_phrases():
+        def a_pause_a_question_pause_a_question_a_question_mark_accent_phrases() -> (
+            list[AccentPhrase]
+        ):
             return [
                 AccentPhrase(
                     moras=[
@@ -538,7 +540,7 @@ def _assert_error_code(self, kana: str, code: ParseKanaErrorCode) -> None:
             parse_kana(kana)
         self.assertEqual(err.exception.errcode, code)
 
-    def test_exceptions(self):
+    def test_exceptions(self) -> None:
         self._assert_error_code("アクセント", ParseKanaErrorCode.ACCENT_NOTFOUND)
         self._assert_error_code("'アクセント", ParseKanaErrorCode.ACCENT_TOP)
         self._assert_error_code("ア'ク'セント", ParseKanaErrorCode.ACCENT_TWICE)
@@ -566,8 +568,8 @@ def test_exceptions(self):
 
 
 class TestCreateKana(TestCase):
-    def test_create_kana_interrogative(self):
-        def koreha_arimasuka_accent_phrases():
+    def test_create_kana_interrogative(self) -> None:
+        def koreha_arimasuka_accent_phrases() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
@@ -656,7 +658,7 @@ def koreha_arimasuka_accent_phrases():
         accent_phrases[-1].is_interrogative = True
         self.assertEqual(create_kana(accent_phrases), "コレワ'/アリマ'_スカ？")
 
-        def kya_accent_phrases():
+        def kya_accent_phrases() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
diff --git a/test/tts_pipeline/test_mora_mapping.py b/test/tts_pipeline/test_mora_mapping.py
index 0791c0ef4..ed327fa6c 100644
--- a/test/tts_pipeline/test_mora_mapping.py
+++ b/test/tts_pipeline/test_mora_mapping.py
@@ -4,7 +4,7 @@
 
 
 class TestOpenJTalkMoraList(TestCase):
-    def test_mora2text(self):
+    def test_mora2text(self) -> None:
         self.assertEqual("ッ", mora_phonemes_to_mora_kana["cl"])
         self.assertEqual("ティ", mora_phonemes_to_mora_kana["ti"])
         self.assertEqual("トゥ", mora_phonemes_to_mora_kana["tu"])
@@ -13,7 +13,7 @@ def test_mora2text(self):
         self.assertEqual("ギェ", mora_phonemes_to_mora_kana["gye"])
         self.assertEqual("イェ", mora_phonemes_to_mora_kana["ye"])
 
-    def test_mora2text_injective(self):
+    def test_mora2text_injective(self) -> None:
         """異なるモーラが同じ読みがなに対応しないか確認する"""
         values = list(mora_phonemes_to_mora_kana.values())
         uniq_values = list(set(values))
diff --git a/test/tts_pipeline/test_phoneme.py b/test/tts_pipeline/test_phoneme.py
index cc6dd8315..e13a39ddb 100644
--- a/test/tts_pipeline/test_phoneme.py
+++ b/test/tts_pipeline/test_phoneme.py
@@ -7,7 +7,7 @@
 TRUE_NUM_PHONEME = 45
 
 
-def test_unknown_phoneme():
+def test_unknown_phoneme() -> None:
     """Unknown音素 `xx` のID取得を拒否する"""
     # Inputs
     unknown_phoneme = Phoneme("xx")
@@ -18,13 +18,13 @@ def test_unknown_phoneme():
 
 
 class TestPhoneme(TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         super().setUp()
         # list_idx      0 1 2 3 4 5  6 7 8 9  10 1 2 3 4 5 6 7 8   9
         hello_hiho = "sil k o N n i ch i w a pau h i h o d e s U sil".split()
         self.ojt_hello_hiho = [Phoneme(s) for s in hello_hiho]
 
-    def test_const(self):
+    def test_const(self) -> None:
         self.assertEqual(Phoneme._NUM_PHONEME, TRUE_NUM_PHONEME)
         self.assertEqual(Phoneme._PHONEME_LIST[1], "A")
         self.assertEqual(Phoneme._PHONEME_LIST[14], "e")
@@ -32,17 +32,17 @@ def test_const(self):
         self.assertEqual(Phoneme._PHONEME_LIST[38], "ts")
         self.assertEqual(Phoneme._PHONEME_LIST[41], "v")
 
-    def test_convert(self):
+    def test_convert(self) -> None:
         sil_phoneme = Phoneme("sil")
         self.assertEqual(sil_phoneme._phoneme, "pau")
 
-    def test_phoneme_id(self):
+    def test_phoneme_id(self) -> None:
         ojt_str_hello_hiho = " ".join([str(p.id) for p in self.ojt_hello_hiho])
         self.assertEqual(
             ojt_str_hello_hiho, "0 23 30 4 28 21 10 21 42 7 0 19 21 19 30 12 14 35 6 0"
         )
 
-    def test_onehot(self):
+    def test_onehot(self) -> None:
         phoneme_id_list = [
             0,
             23,
diff --git a/test/tts_pipeline/test_text_analyzer.py b/test/tts_pipeline/test_text_analyzer.py
index ebaf30977..29f9ed652 100644
--- a/test/tts_pipeline/test_text_analyzer.py
+++ b/test/tts_pipeline/test_text_analyzer.py
@@ -40,7 +40,7 @@ def features(ojt_container: OjtContainer) -> list[str]:
 
 
 class TestBaseLabels(TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         super().setUp()
         # pyopenjtalk.extract_fullcontext("こんにちは、ヒホです。")の結果
         # 出来る限りテスト内で他のライブラリに依存しないため、
@@ -143,14 +143,14 @@ def space_jointed_phonemes(ojt_container: OjtContainer) -> str:
 
 
 class TestLabel(TestBaseLabels):
-    def test_phoneme(self):
+    def test_phoneme(self) -> None:
         """Label に含まれる音素をテスト"""
         self.assertEqual(
             " ".join([label.phoneme for label in self.labels_hello_hiho]),
             "sil k o N n i ch i w a pau h i h o d e s U sil",
         )
 
-    def test_is_pause(self):
+    def test_is_pause(self) -> None:
         """Label のポーズ判定をテスト"""
         self.assertEqual(
             [label.is_pause() for label in self.labels_hello_hiho],
@@ -262,19 +262,19 @@ def setUp(self) -> None:
             self.labels_hello_hiho[11:19]
         )
 
-    def test_accent(self):
+    def test_accent(self) -> None:
         """AccentPhraseLabel に含まれるアクセント位置をテスト"""
         self.assertEqual(self.accent_phrase_hello.accent, 5)
         self.assertEqual(self.accent_phrase_hiho.accent, 1)
 
-    def test_phonemes(self):
+    def test_phonemes(self) -> None:
         """AccentPhraseLabel に含まれる音素系列をテスト"""
         outputs_hello = space_jointed_phonemes(self.accent_phrase_hello)
         outputs_hiho = space_jointed_phonemes(self.accent_phrase_hiho)
         self.assertEqual(outputs_hello, "k o N n i ch i w a")
         self.assertEqual(outputs_hiho, "h i h o d e s U")
 
-    def test_features(self):
+    def test_features(self) -> None:
         """AccentPhraseLabel に含まれる features をテスト"""
         expects = self.test_case_hello_hiho
         self.assertEqual(features(self.accent_phrase_hello), expects[1:10])
@@ -291,14 +291,14 @@ def setUp(self) -> None:
             self.labels_hello_hiho[11:19]
         )
 
-    def test_phonemes(self):
+    def test_phonemes(self) -> None:
         """BreathGroupLabel に含まれる音素系列をテスト"""
         outputs_hello = space_jointed_phonemes(self.breath_group_hello)
         outputs_hiho = space_jointed_phonemes(self.breath_group_hiho)
         self.assertEqual(outputs_hello, "k o N n i ch i w a")
         self.assertEqual(outputs_hiho, "h i h o d e s U")
 
-    def test_features(self):
+    def test_features(self) -> None:
         """BreathGroupLabel に含まれる features をテスト"""
         expects = self.test_case_hello_hiho
         self.assertEqual(features(self.breath_group_hello), expects[1:10])
@@ -310,19 +310,19 @@ def setUp(self) -> None:
         super().setUp()
         self.utterance_hello_hiho = UtteranceLabel.from_labels(self.labels_hello_hiho)
 
-    def test_phonemes(self):
+    def test_phonemes(self) -> None:
         """UtteranceLabel に含まれる音素系列をテスト"""
         outputs_hello_hiho = space_jointed_phonemes(self.utterance_hello_hiho)
         expects_hello_hiho = "sil k o N n i ch i w a pau h i h o d e s U sil"
         self.assertEqual(outputs_hello_hiho, expects_hello_hiho)
 
-    def test_features(self):
+    def test_features(self) -> None:
         """UtteranceLabel に含まれる features をテスト"""
         self.assertEqual(features(self.utterance_hello_hiho), self.test_case_hello_hiho)
 
 
 class TestMoraToText(TestCase):
-    def test_voice(self):
+    def test_voice(self) -> None:
         self.assertEqual(mora_to_text("a"), "ア")
         self.assertEqual(mora_to_text("i"), "イ")
         self.assertEqual(mora_to_text("ka"), "カ")
@@ -332,7 +332,7 @@ def test_voice(self):
         self.assertEqual(mora_to_text("ye"), "イェ")
         self.assertEqual(mora_to_text("wo"), "ウォ")
 
-    def test_unvoice(self):
+    def test_unvoice(self) -> None:
         self.assertEqual(mora_to_text("A"), "ア")
         self.assertEqual(mora_to_text("I"), "イ")
         self.assertEqual(mora_to_text("kA"), "カ")
@@ -340,7 +340,7 @@ def test_unvoice(self):
         self.assertEqual(mora_to_text("yE"), "イェ")
         self.assertEqual(mora_to_text("wO"), "ウォ")
 
-    def test_invalid_mora(self):
+    def test_invalid_mora(self) -> None:
         """変なモーラが来ても例外を投げない"""
         self.assertEqual(mora_to_text("x"), "x")
         self.assertEqual(mora_to_text(""), "")
@@ -357,7 +357,7 @@ def _gen_mora(text: str, consonant: str | None, vowel: str) -> Mora:
     )
 
 
-def test_text_to_accent_phrases_normal():
+def test_text_to_accent_phrases_normal() -> None:
     """`text_to_accent_phrases` は正常な日本語文をパースする"""
     # Inputs
     text = "こんにちは、ヒホです。"
@@ -402,7 +402,7 @@ def stub_unknown_features_koxx(_: str) -> list[str]:
     ]
 
 
-def test_text_to_accent_phrases_unknown():
+def test_text_to_accent_phrases_unknown() -> None:
     """`text_to_accent_phrases` は unknown 音素を含む features をパースする"""
     # Expects
     true_accent_phrases = [
diff --git a/test/tts_pipeline/test_tts_engine.py b/test/tts_pipeline/test_tts_engine.py
index 8d4c322b6..57598155b 100644
--- a/test/tts_pipeline/test_tts_engine.py
+++ b/test/tts_pipeline/test_tts_engine.py
@@ -93,13 +93,13 @@ class MockCore:
     yukarin_sa_forward = Mock(side_effect=yukarin_sa_mock)
     decode_forward = Mock(side_effect=decode_mock)
 
-    def metas(self):
+    def metas(self) -> str:
         return ""
 
-    def supported_devices(self):
+    def supported_devices(self) -> str:
         return ""
 
-    def is_model_loaded(self, style_id):
+    def is_model_loaded(self, style_id: str) -> bool:
         return True
 
 
@@ -122,7 +122,7 @@ def _gen_mora(
     )
 
 
-def test_to_flatten_phonemes():
+def test_to_flatten_phonemes() -> None:
     """Test `to_flatten_phonemes`."""
     # Inputs
     moras = [
@@ -205,7 +205,7 @@ def _gen_doremi_score() -> Score:
 
 
 class TestTTSEngine(TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         super().setUp()
         core = MockCore()
         self.yukarin_s_mock = core.yukarin_s_forward
@@ -213,7 +213,7 @@ def setUp(self):
         self.decode_mock = core.decode_forward
         self.tts_engine = TTSEngine(core=core)  # type: ignore[arg-type]
 
-    def test_to_flatten_moras(self):
+    def test_to_flatten_moras(self) -> None:
         flatten_moras = to_flatten_moras(_gen_hello_hiho_accent_phrases())
         true_accent_phrases_hello_hiho = _gen_hello_hiho_accent_phrases()
         self.assertEqual(
@@ -223,7 +223,7 @@ def test_to_flatten_moras(self):
             + true_accent_phrases_hello_hiho[1].moras,
         )
 
-    def test_update_length(self):
+    def test_update_length(self) -> None:
         # Inputs
         hello_hiho = _gen_hello_hiho_accent_phrases()
         # Indirect Outputs（yukarin_sに渡される値）
@@ -247,7 +247,7 @@ def test_update_length(self):
             np.array(true_phoneme_list, dtype=np.int64),
         )
 
-    def test_update_pitch(self):
+    def test_update_pitch(self) -> None:
         # 空のリストでエラーを吐かないか
         # Inputs
         phrases: list = []
@@ -296,7 +296,7 @@ def test_update_pitch(self):
         np.testing.assert_array_equal(end_accent_phrase_list, true_phrase_ends)
 
 
-def test_create_accent_phrases_toward_unknown():
+def test_create_accent_phrases_toward_unknown() -> None:
     """`TTSEngine.create_accent_phrases()` は unknown 音素の Phoneme 化に失敗する"""
     engine = TTSEngine(MockCoreWrapper())
 
@@ -416,7 +416,7 @@ def test_mocked_synthesize_wave_from_score_output(
     )
 
 
-def koreha_arimasuka_base_expected():
+def koreha_arimasuka_base_expected() -> list[AccentPhrase]:
     return [
         AccentPhrase(
             moras=[
@@ -500,7 +500,7 @@ def koreha_arimasuka_base_expected():
 
 
 class TestTTSEngineBase(TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         super().setUp()
         self.tts_engine = TTSEngine(core=MockCoreWrapper())
 
@@ -517,7 +517,7 @@ def create_synthesis_test_base(
         outputs = apply_interrogative_upspeak(inputs, enable_interrogative_upspeak)
         self.assertEqual(expected, outputs, f"case(text:{text})")
 
-    def test_create_accent_phrases(self):
+    def test_create_accent_phrases(self) -> None:
         """accent_phrasesの作成時では疑問文モーラ処理を行わない
         (https://github.com/VOICEVOX/voicevox_engine/issues/272#issuecomment-1022610866)
         """
@@ -527,7 +527,7 @@ def test_create_accent_phrases(self):
         actual = self.tts_engine.create_accent_phrases(text, StyleId(1))
         self.assertEqual(expected, actual, f"case(text:{text})")
 
-    def test_upspeak_voiced_last_mora(self):
+    def test_upspeak_voiced_last_mora(self) -> None:
         # voiced + "？" + flagON -> upspeak
         expected = koreha_arimasuka_base_expected()
         expected[-1].is_interrogative = True
@@ -564,8 +564,8 @@ def test_upspeak_voiced_last_mora(self):
             enable_interrogative_upspeak=True,
         )
 
-    def test_upspeak_voiced_N_last_mora(self):
-        def nn_base_expected():
+    def test_upspeak_voiced_N_last_mora(self) -> None:
+        def nn_base_expected() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
@@ -620,8 +620,8 @@ def nn_base_expected():
             enable_interrogative_upspeak=False,
         )
 
-    def test_upspeak_unvoiced_last_mora(self):
-        def ltu_base_expected():
+    def test_upspeak_unvoiced_last_mora(self) -> None:
+        def ltu_base_expected() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
@@ -666,8 +666,8 @@ def ltu_base_expected():
             enable_interrogative_upspeak=False,
         )
 
-    def test_upspeak_voiced_u_last_mora(self):
-        def su_base_expected():
+    def test_upspeak_voiced_u_last_mora(self) -> None:
+        def su_base_expected() -> list[AccentPhrase]:
             return [
                 AccentPhrase(
                     moras=[
diff --git a/test/tts_pipeline/test_wave_synthesizer.py b/test/tts_pipeline/test_wave_synthesizer.py
index 084edcec6..fdddb2f6b 100644
--- a/test/tts_pipeline/test_wave_synthesizer.py
+++ b/test/tts_pipeline/test_wave_synthesizer.py
@@ -64,7 +64,7 @@ def _gen_mora(
     )
 
 
-def test_apply_prepost_silence():
+def test_apply_prepost_silence() -> None:
     """Test `apply_prepost_silence`."""
     # Inputs
     query = _gen_query(prePhonemeLength=2 * 0.01067, postPhonemeLength=6 * 0.01067)
@@ -85,7 +85,7 @@ def test_apply_prepost_silence():
     assert moras_with_silence == true_moras_with_silence
 
 
-def test_apply_speed_scale():
+def test_apply_speed_scale() -> None:
     """Test `apply_speed_scale`."""
     # Inputs
     query = _gen_query(speedScale=2.0)
@@ -112,7 +112,7 @@ def test_apply_speed_scale():
     assert moras == true_moras
 
 
-def test_apply_pitch_scale():
+def test_apply_pitch_scale() -> None:
     """Test `apply_pitch_scale`."""
     # Inputs
     query = _gen_query(pitchScale=2.0)
@@ -139,7 +139,7 @@ def test_apply_pitch_scale():
     assert moras == true_moras
 
 
-def test_apply_intonation_scale():
+def test_apply_intonation_scale() -> None:
     """Test `apply_intonation_scale`."""
     # Inputs
     query = _gen_query(intonationScale=0.5)
@@ -166,7 +166,7 @@ def test_apply_intonation_scale():
     assert moras == true_moras
 
 
-def test_apply_volume_scale():
+def test_apply_volume_scale() -> None:
     """Test `apply_volume_scale`."""
     # Inputs
     query = _gen_query(volumeScale=3.0)
@@ -181,7 +181,7 @@ def test_apply_volume_scale():
     assert np.allclose(wave, true_wave)
 
 
-def test_apply_output_sampling_rate():
+def test_apply_output_sampling_rate() -> None:
     """Test `apply_output_sampling_rate`."""
     # Inputs
     query = _gen_query(outputSamplingRate=12000)
@@ -198,7 +198,7 @@ def test_apply_output_sampling_rate():
     assert wave.shape[0] == true_wave.shape[0]
 
 
-def test_apply_output_stereo():
+def test_apply_output_stereo() -> None:
     """Test `apply_output_stereo`."""
     # Inputs
     query = _gen_query(outputStereo=True)
@@ -213,7 +213,7 @@ def test_apply_output_stereo():
     assert np.array_equal(wave, true_wave)
 
 
-def test_count_frame_per_unit():
+def test_count_frame_per_unit() -> None:
     """Test `count_frame_per_unit`."""
     # Inputs
     moras = [
@@ -241,7 +241,7 @@ def test_count_frame_per_unit():
     assert np.array_equal(frame_per_mora, true_frame_per_mora)
 
 
-def test_query_to_decoder_feature():
+def test_query_to_decoder_feature() -> None:
     """Test `query_to_decoder_feature`."""
     # Inputs
     accent_phrases = [
@@ -300,7 +300,7 @@ def test_query_to_decoder_feature():
     assert np.array_equal(f0, true_f0)
 
 
-def test_raw_wave_to_output_wave_with_resample():
+def test_raw_wave_to_output_wave_with_resample() -> None:
     """Test `raw_wave_to_output_wave` with resampling option."""
     # Inputs
     query = _gen_query(volumeScale=2, outputSamplingRate=48000, outputStereo=True)
@@ -316,7 +316,7 @@ def test_raw_wave_to_output_wave_with_resample():
     assert wave.shape == true_wave_shape
 
 
-def test_raw_wave_to_output_wave_without_resample():
+def test_raw_wave_to_output_wave_without_resample() -> None:
     """Test `raw_wave_to_output_wave`  without resampling option."""
     # Inputs
     query = _gen_query(volumeScale=2, outputStereo=True)
diff --git a/test/user_dict/test_user_dict.py b/test/user_dict/test_user_dict.py
index 446156eea..cb938a689 100644
--- a/test/user_dict/test_user_dict.py
+++ b/test/user_dict/test_user_dict.py
@@ -76,21 +76,21 @@ def get_new_word(user_dict: dict[str, UserDictWord]) -> UserDictWord:
 
 
 class TestUserDict(TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         self.tmp_dir = TemporaryDirectory()
         self.tmp_dir_path = Path(self.tmp_dir.name)
 
-    def tearDown(self):
+    def tearDown(self) -> None:
         unset_user_dict()
         self.tmp_dir.cleanup()
 
-    def test_read_not_exist_json(self):
+    def test_read_not_exist_json(self) -> None:
         self.assertEqual(
             read_dict(user_dict_path=(self.tmp_dir_path / "not_exist.json")),
             {},
         )
 
-    def test_create_word(self):
+    def test_create_word(self) -> None:
         # 将来的に品詞などが追加された時にテストを増やす
         self.assertEqual(
             _create_word(surface="test", pronunciation="テスト", accent_type=1),
@@ -112,7 +112,7 @@ def test_create_word(self):
             ),
         )
 
-    def test_apply_word_without_json(self):
+    def test_apply_word_without_json(self) -> None:
         user_dict_path = self.tmp_dir_path / "test_apply_word_without_json.json"
         apply_word(
             surface="test",
@@ -133,7 +133,7 @@ def test_apply_word_without_json(self):
             ("ｔｅｓｔ", "テスト", 1),
         )
 
-    def test_apply_word_with_json(self):
+    def test_apply_word_with_json(self) -> None:
         user_dict_path = self.tmp_dir_path / "test_apply_word_with_json.json"
         user_dict_path.write_text(
             json.dumps(valid_dict_dict_json, ensure_ascii=False), encoding="utf-8"
@@ -157,7 +157,7 @@ def test_apply_word_with_json(self):
             ("ｔｅｓｔ２", "テストツー", 3),
         )
 
-    def test_rewrite_word_invalid_id(self):
+    def test_rewrite_word_invalid_id(self) -> None:
         user_dict_path = self.tmp_dir_path / "test_rewrite_word_invalid_id.json"
         user_dict_path.write_text(
             json.dumps(valid_dict_dict_json, ensure_ascii=False), encoding="utf-8"
@@ -173,7 +173,7 @@ def test_rewrite_word_invalid_id(self):
             compiled_dict_path=(self.tmp_dir_path / "test_rewrite_word_invalid_id.dic"),
         )
 
-    def test_rewrite_word_valid_id(self):
+    def test_rewrite_word_valid_id(self) -> None:
         user_dict_path = self.tmp_dir_path / "test_rewrite_word_valid_id.json"
         user_dict_path.write_text(
             json.dumps(valid_dict_dict_json, ensure_ascii=False), encoding="utf-8"
@@ -194,7 +194,7 @@ def test_rewrite_word_valid_id(self):
             ("ｔｅｓｔ２", "テストツー", 2),
         )
 
-    def test_delete_word_invalid_id(self):
+    def test_delete_word_invalid_id(self) -> None:
         user_dict_path = self.tmp_dir_path / "test_delete_word_invalid_id.json"
         user_dict_path.write_text(
             json.dumps(valid_dict_dict_json, ensure_ascii=False), encoding="utf-8"
@@ -207,7 +207,7 @@ def test_delete_word_invalid_id(self):
             compiled_dict_path=(self.tmp_dir_path / "test_delete_word_invalid_id.dic"),
         )
 
-    def test_delete_word_valid_id(self):
+    def test_delete_word_valid_id(self) -> None:
         user_dict_path = self.tmp_dir_path / "test_delete_word_valid_id.json"
         user_dict_path.write_text(
             json.dumps(valid_dict_dict_json, ensure_ascii=False), encoding="utf-8"
@@ -219,7 +219,7 @@ def test_delete_word_valid_id(self):
         )
         self.assertEqual(len(read_dict(user_dict_path=user_dict_path)), 0)
 
-    def test_priority(self):
+    def test_priority(self) -> None:
         for pos in part_of_speech_data:
             for i in range(MAX_PRIORITY + 1):
                 self.assertEqual(
@@ -233,7 +233,7 @@ def test_priority(self):
                     i,
                 )
 
-    def test_import_dict(self):
+    def test_import_dict(self) -> None:
         user_dict_path = self.tmp_dir_path / "test_import_dict.json"
         compiled_dict_path = self.tmp_dir_path / "test_import_dict.dic"
         user_dict_path.write_text(
@@ -254,7 +254,7 @@ def test_import_dict(self):
             UserDictWord(**valid_dict_dict_api["aab7dda2-0d97-43c8-8cb7-3f440dab9b4e"]),
         )
 
-    def test_import_dict_no_override(self):
+    def test_import_dict_no_override(self) -> None:
         user_dict_path = self.tmp_dir_path / "test_import_dict_no_override.json"
         compiled_dict_path = self.tmp_dir_path / "test_import_dict_no_override.dic"
         user_dict_path.write_text(
@@ -271,7 +271,7 @@ def test_import_dict_no_override(self):
             UserDictWord(**valid_dict_dict_api["aab7dda2-0d97-43c8-8cb7-3f440dab9b4e"]),
         )
 
-    def test_import_dict_override(self):
+    def test_import_dict_override(self) -> None:
         user_dict_path = self.tmp_dir_path / "test_import_dict_override.json"
         compiled_dict_path = self.tmp_dir_path / "test_import_dict_override.dic"
         user_dict_path.write_text(
@@ -288,7 +288,7 @@ def test_import_dict_override(self):
             import_word,
         )
 
-    def test_import_invalid_word(self):
+    def test_import_invalid_word(self) -> None:
         user_dict_path = self.tmp_dir_path / "test_import_invalid_dict.json"
         compiled_dict_path = self.tmp_dir_path / "test_import_invalid_dict.dic"
         invalid_accent_associative_rule_word = deepcopy(import_word)
@@ -321,7 +321,7 @@ def test_import_invalid_word(self):
             compiled_dict_path=compiled_dict_path,
         )
 
-    def test_update_dict(self):
+    def test_update_dict(self) -> None:
         user_dict_path = self.tmp_dir_path / "test_update_dict.json"
         compiled_dict_path = self.tmp_dir_path / "test_update_dict.dic"
         update_dict(
diff --git a/test/user_dict/test_user_dict_model.py b/test/user_dict/test_user_dict_model.py
index 2c00309b4..686cd0893 100644
--- a/test/user_dict/test_user_dict_model.py
+++ b/test/user_dict/test_user_dict_model.py
@@ -44,26 +44,26 @@ def generate_model() -> TestModel:
 
 
 class TestUserDictWords(TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         pass
 
-    def test_valid_word(self):
+    def test_valid_word(self) -> None:
         test_value = generate_model()
         try:
             UserDictWord(**test_value)
         except ValidationError as e:
             self.fail(f"Unexpected Validation Error\n{str(e)}")
 
-    def test_convert_to_zenkaku(self):
+    def test_convert_to_zenkaku(self) -> None:
         test_value = generate_model()
         test_value["surface"] = "test"
         self.assertEqual(UserDictWord(**test_value).surface, "ｔｅｓｔ")
 
-    def test_count_mora(self):
+    def test_count_mora(self) -> None:
         test_value = generate_model()
         self.assertEqual(UserDictWord(**test_value).mora_count, 3)
 
-    def test_count_mora_x(self):
+    def test_count_mora_x(self) -> None:
         test_value = generate_model()
         for s in [chr(i) for i in range(12449, 12533)]:
             if s in ["ァ", "ィ", "ゥ", "ェ", "ォ", "ッ", "ャ", "ュ", "ョ", "ヮ"]:
@@ -81,7 +81,7 @@ def test_count_mora_x(self):
                         expected_count,
                     )
 
-    def test_count_mora_xwa(self):
+    def test_count_mora_xwa(self) -> None:
         test_value = generate_model()
         test_value["pronunciation"] = "クヮンセイ"
         expected_count = 0
@@ -94,36 +94,36 @@ def test_count_mora_xwa(self):
             expected_count,
         )
 
-    def test_invalid_pronunciation_not_katakana(self):
+    def test_invalid_pronunciation_not_katakana(self) -> None:
         test_value = generate_model()
         test_value["pronunciation"] = "ぼいぼ"
         with self.assertRaises(ValidationError):
             UserDictWord(**test_value)
 
-    def test_invalid_pronunciation_invalid_sutegana(self):
+    def test_invalid_pronunciation_invalid_sutegana(self) -> None:
         test_value = generate_model()
         test_value["pronunciation"] = "アィウェォ"
         with self.assertRaises(ValidationError):
             UserDictWord(**test_value)
 
-    def test_invalid_pronunciation_invalid_xwa(self):
+    def test_invalid_pronunciation_invalid_xwa(self) -> None:
         test_value = generate_model()
         test_value["pronunciation"] = "アヮ"
         with self.assertRaises(ValidationError):
             UserDictWord(**test_value)
 
-    def test_count_mora_voiced_sound(self):
+    def test_count_mora_voiced_sound(self) -> None:
         test_value = generate_model()
         test_value["pronunciation"] = "ボイボ"
         self.assertEqual(UserDictWord(**test_value).mora_count, 3)
 
-    def test_invalid_accent_type(self):
+    def test_invalid_accent_type(self) -> None:
         test_value = generate_model()
         test_value["accent_type"] = 4
         with self.assertRaises(ValidationError):
             UserDictWord(**test_value)
 
-    def test_invalid_accent_type_2(self):
+    def test_invalid_accent_type_2(self) -> None:
         test_value = generate_model()
         test_value["accent_type"] = -1
         with self.assertRaises(ValidationError):
diff --git a/test/user_dict/test_word_types.py b/test/user_dict/test_word_types.py
index e26ce192f..0e64dd10d 100644
--- a/test/user_dict/test_word_types.py
+++ b/test/user_dict/test_word_types.py
@@ -5,5 +5,5 @@
 
 
 class TestWordTypes(TestCase):
-    def test_word_types(self):
+    def test_word_types(self) -> None:
         self.assertCountEqual(list(WordTypes), list(part_of_speech_data.keys()))
diff --git a/voicevox_engine/dev/core/mock.py b/voicevox_engine/dev/core/mock.py
index 25190ea55..8833ad0df 100644
--- a/voicevox_engine/dev/core/mock.py
+++ b/voicevox_engine/dev/core/mock.py
@@ -228,7 +228,7 @@ def sf_decode_forward(
             ] * 256
         return np.array(result, dtype=np.float32)
 
-    def supported_devices(self):
+    def supported_devices(self) -> str:
         return json.dumps(
             {
                 "cpu": True,
diff --git a/voicevox_engine/dev/tts_engine/mock.py b/voicevox_engine/dev/tts_engine/mock.py
index 9373cb0ce..fc4e4d415 100644
--- a/voicevox_engine/dev/tts_engine/mock.py
+++ b/voicevox_engine/dev/tts_engine/mock.py
@@ -16,7 +16,7 @@
 class MockTTSEngine(TTSEngine):
     """製品版コア無しに音声合成が可能なモック版TTSEngine"""
 
-    def __init__(self):
+    def __init__(self) -> None:
         super().__init__(MockCoreWrapper())
 
     def synthesize_wave(
diff --git a/voicevox_engine/model.py b/voicevox_engine/model.py
index b0013b1b0..892753865 100644
--- a/voicevox_engine/model.py
+++ b/voicevox_engine/model.py
@@ -21,7 +21,7 @@ class Mora(BaseModel):
         title="音高"
     )  # デフォルト値をつけるとts側のOpenAPIで生成されたコードの型がOptionalになる
 
-    def __hash__(self):
+    def __hash__(self) -> int:
         items = [
             (k, tuple(v)) if isinstance(v, List) else (k, v)
             for k, v in self.__dict__.items()
@@ -42,7 +42,7 @@ class AccentPhrase(BaseModel):
     pause_mora: Optional[Mora] = Field(title="後ろに無音を付けるかどうか")
     is_interrogative: bool = Field(default=False, title="疑問系かどうか")
 
-    def __hash__(self):
+    def __hash__(self) -> int:
         items = [
             (k, tuple(v)) if isinstance(v, List) else (k, v)
             for k, v in self.__dict__.items()
@@ -68,7 +68,7 @@ class AudioQuery(BaseModel):
         title="[読み取り専用]AquesTalk 風記法によるテキスト。音声合成用のクエリとしては無視される"
     )
 
-    def __hash__(self):
+    def __hash__(self) -> int:
         items = [
             (k, tuple(v)) if isinstance(v, List) else (k, v)
             for k, v in self.__dict__.items()
diff --git a/voicevox_engine/preset/PresetManager.py b/voicevox_engine/preset/PresetManager.py
index cfb8dc161..c554e3e46 100644
--- a/voicevox_engine/preset/PresetManager.py
+++ b/voicevox_engine/preset/PresetManager.py
@@ -174,7 +174,7 @@ def delete_preset(self, id: int) -> int:
 
         return id
 
-    def _write_on_file(self):
+    def _write_on_file(self) -> None:
         """プリセット情報のファイル（簡易データベース）書き込み"""
         with open(self.preset_path, mode="w", encoding="utf-8") as f:
             yaml.safe_dump(
diff --git a/voicevox_engine/tts_pipeline/text_analyzer.py b/voicevox_engine/tts_pipeline/text_analyzer.py
index 70ea83b12..dd9981074 100644
--- a/voicevox_engine/tts_pipeline/text_analyzer.py
+++ b/voicevox_engine/tts_pipeline/text_analyzer.py
@@ -115,7 +115,7 @@ def breath_group_index(self) -> str:
         """BreathGroupのインデックス"""
         return self.contexts["i3"]
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return f"<Label phoneme='{self.phoneme}'>"
 
 
diff --git a/voicevox_engine/utility/path_utility.py b/voicevox_engine/utility/path_utility.py
index 7c46ad40b..0091cd52a 100644
--- a/voicevox_engine/utility/path_utility.py
+++ b/voicevox_engine/utility/path_utility.py
@@ -33,7 +33,7 @@ def is_development() -> bool:
     return True
 
 
-def get_save_dir():
+def get_save_dir() -> Path:
     # FIXME: ファイル保存場所をエンジン固有のIDが入ったものにする
     # FIXME: Windowsは`voicevox-engine/voicevox-engine`ディレクトリに保存されているので
     # `VOICEVOX/voicevox-engine`に変更する