diff --git a/packages/backend/src/core/CacheService.ts b/packages/backend/src/core/CacheService.ts
index 152e70972e..c997095eb8 100644
--- a/packages/backend/src/core/CacheService.ts
+++ b/packages/backend/src/core/CacheService.ts
@@ -460,21 +460,25 @@ export class CacheService implements OnApplicationShutdown {
 	}
 
 	@bindThis
-	public async findLocalUserById(userId: MiUser['id']): Promise<MiLocalUser | null> {
-		return await this.localUserByIdCache.fetchMaybe(userId, async () => {
-			return await this.usersRepository.findOneBy({ id: userId, host: IsNull() }) as MiLocalUser | null ?? undefined;
-		}) ?? null;
+	public async findLocalUserById(userId: MiUser['id']): Promise<MiLocalUser> {
+		const user = await this.findUserById(userId);
+
+		if (!isLocalUser(user)) {
+			throw new IdentifiableError('aeac1339-2550-4521-a8e3-781f06d98656', 'User is not local');
+		}
+
+		return user;
 	}
 
 	@bindThis
-	public async findRemoteUserById(userId: MiUser['id']): Promise<MiRemoteUser | null> {
+	public async findRemoteUserById(userId: MiUser['id']): Promise<MiRemoteUser> {
 		const user = await this.findUserById(userId);
 
-		if (user.host == null) {
-			return null;
+		if (!isRemoteUser(user)) {
+			throw new IdentifiableError('aeac1339-2550-4521-a8e3-781f06d98656', 'User is not remote');
 		}
 
-		return user as MiRemoteUser;
+		return user;
 	}
 
 	@bindThis
diff --git a/packages/backend/src/core/NoteCreateService.ts b/packages/backend/src/core/NoteCreateService.ts
index a18aaebebd..7771c08544 100644
--- a/packages/backend/src/core/NoteCreateService.ts
+++ b/packages/backend/src/core/NoteCreateService.ts
@@ -199,7 +199,6 @@ export class NoteCreateService implements OnApplicationShutdown {
 		@Inject(DI.channelFollowingsRepository)
 		private channelFollowingsRepository: ChannelFollowingsRepository,
 
-		private userEntityService: UserEntityService,
 		private noteEntityService: NoteEntityService,
 		private idService: IdService,
 		private globalEventService: GlobalEventService,
@@ -676,7 +675,7 @@ export class NoteCreateService implements OnApplicationShutdown {
 		}
 
 		if (!silent) {
-			if (this.isLocalUser(user)) this.activeUsersChart.write(user);
+			if (isLocalUser(user)) this.activeUsersChart.write(user);
 
 			// Pack the note
 			const noteObj = await this.noteEntityService.pack(note, null, { skipHide: true, withReactionAndUserPairCache: true });
diff --git a/packages/backend/src/core/activitypub/models/ApNoteService.ts b/packages/backend/src/core/activitypub/models/ApNoteService.ts
index 9b1293d09a..a2f53a787e 100644
--- a/packages/backend/src/core/activitypub/models/ApNoteService.ts
+++ b/packages/backend/src/core/activitypub/models/ApNoteService.ts
@@ -9,7 +9,7 @@ import { UnrecoverableError } from 'bullmq';
 import promiseLimit from 'promise-limit';
 import { ModuleRef } from '@nestjs/core';
 import { DI } from '@/di-symbols.js';
-import type { PollsRepository, EmojisRepository, NotesRepository, MiMeta } from '@/models/_.js';
+import type { UsersRepository, PollsRepository, EmojisRepository, NotesRepository, MiMeta } from '@/models/_.js';
 import type { Config } from '@/config.js';
 import type { MiRemoteUser } from '@/models/User.js';
 import type { MiNote } from '@/models/Note.js';
@@ -33,8 +33,7 @@ import { extractMediaFromHtml } from '@/core/activitypub/misc/extract-media-from
 import { extractMediaFromMfm } from '@/core/activitypub/misc/extract-media-from-mfm.js';
 import { getContentByType } from '@/core/activitypub/misc/get-content-by-type.js';
 import { CustomEmojiService, encodeEmojiKey, isValidEmojiName } from '@/core/CustomEmojiService.js';
-import { fromTuple } from '@/misc/from-tuple.js';
-import { getOneApId, getApId, isEmoji, getApType, isApObject, isDocument, IApDocument, isLink, isQuestion, getNullableApId, isPost } from '../type.js';
+import { getOneApId, getApId, validPost, isEmoji, getApType, isApObject, isDocument, IApDocument, isLink } from '../type.js';
 import { ApLoggerService } from '../ApLoggerService.js';
 import { ApMfmService } from '../ApMfmService.js';
 import { ApDbResolverService } from '../ApDbResolverService.js';
@@ -63,6 +62,9 @@ export class ApNoteService implements OnModuleInit {
 		@Inject(DI.meta)
 		private meta: MiMeta,
 
+		@Inject(DI.usersRepository)
+		private usersRepository: UsersRepository,
+
 		@Inject(DI.pollsRepository)
 		private pollsRepository: PollsRepository,
 
diff --git a/packages/backend/test/e2e/reversi-game.ts b/packages/backend/test/e2e/reversi-game.ts
index 788255beac..c1f30a8f4c 100644
--- a/packages/backend/test/e2e/reversi-game.ts
+++ b/packages/backend/test/e2e/reversi-game.ts
@@ -6,7 +6,6 @@
 process.env.NODE_ENV = 'test';
 
 import * as assert from 'assert';
-import { ReversiMatchResponse } from 'misskey-js/entities.js';
 import { api, signup } from '../utils.js';
 import type * as misskey from 'misskey-js';
 
@@ -26,7 +25,7 @@ describe('ReversiGame', () => {
 		const response2 = await api('reversi/match', { userId: alice.id }, bob);
 		assert.strictEqual(response2.status, 200);
 		assert.notStrictEqual(response2.body, null);
-		const body = response2.body as ReversiMatchResponse;
+		const body = response2.body as misskey.entities.ReversiMatchResponse;
 		assert.strictEqual(body.user1.id, alice.id);
 		assert.strictEqual(body.user2.id, bob.id);
 	});