diff --git a/packages/backend/src/server/api/endpoints/flash/show.ts b/packages/backend/src/server/api/endpoints/flash/show.ts
index 210a93edbd..14720a8c8d 100644
--- a/packages/backend/src/server/api/endpoints/flash/show.ts
+++ b/packages/backend/src/server/api/endpoints/flash/show.ts
@@ -1,11 +1,5 @@
-/*
- * SPDX-FileCopyrightText: syuilo and other misskey contributors
- * SPDX-License-Identifier: AGPL-3.0-only
- */
-
-import { IsNull } from 'typeorm';
 import { Inject, Injectable } from '@nestjs/common';
-import type { UsersRepository, FlashsRepository, Flash } from '@/models/index.js';
+import type { UsersRepository, FlashsRepository } from '@/models/index.js';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import { FlashEntityService } from '@/core/entities/FlashEntityService.js';
 import { DI } from '@/di-symbols.js';
@@ -35,39 +29,24 @@ export const paramDef = {
 	type: 'object',
 	properties: {
 		flashId: { type: 'string', format: 'misskey:id' },
-		username: { type: 'string' },
 	},
-	anyOf: [
-		{ required: ['flashId'] },
-		{ required: ['username'] },
-	],
+	required: ['flashId'],
 } as const;
 
 // eslint-disable-next-line import/no-default-export
 @Injectable()
 export default class extends Endpoint<typeof meta, typeof paramDef> {
 	constructor(
+		@Inject(DI.usersRepository)
+		private usersRepository: UsersRepository,
+
 		@Inject(DI.flashsRepository)
 		private flashsRepository: FlashsRepository,
 
 		private flashEntityService: FlashEntityService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
-			let flash: Flash | null = null;
-			if (ps.flashId) {
-				flash = await this.flashsRepository.findOneBy({ id: ps.flashId });
-			}
-			else if (ps.username) {
-				const author = await this.usersRepository.findOneBy({
-					host: IsNull(),
-					usernameLower: ps.username.toLowerCase(),
-				});
-				if (author) {
-					flash = await this.flashsRepository.findOneBy({
-						userId: author.id,
-					});
-				}
-			}
+			const flash = await this.flashsRepository.findOneBy({ id: ps.flashId });
 
 			if (flash == null) {
 				throw new ApiError(meta.errors.noSuchFlash);