diff --git a/packages/backend/src/core/SystemAccountService.ts b/packages/backend/src/core/SystemAccountService.ts
index 4805847788..710e797213 100644
--- a/packages/backend/src/core/SystemAccountService.ts
+++ b/packages/backend/src/core/SystemAccountService.ts
@@ -66,7 +66,7 @@ export class SystemAccountService {
 			return systemAccount.user as MiLocalUser;
 		} else {
 			const created = await this.createCorrespondingUser(type, {
-				username: `system.${type}`, // NOTE: (できれば避けたいが)system.から始まるかどうかでシステムアカウントかどうかを判定している処理もあるので変えないように
+				username: `system.${type}`, // NOTE: (できれば避けたいが) . が含まれるかどうかでシステムアカウントかどうかを判定している処理もあるので変えないように
 				name: this.meta.name,
 			});
 			this.cache.set(type, created);
diff --git a/packages/backend/src/core/entities/UserEntityService.ts b/packages/backend/src/core/entities/UserEntityService.ts
index fbd3892dd4..69f698d9cb 100644
--- a/packages/backend/src/core/entities/UserEntityService.ts
+++ b/packages/backend/src/core/entities/UserEntityService.ts
@@ -28,6 +28,7 @@ import type {
 	FollowingsRepository,
 	FollowRequestsRepository,
 	MiFollowing,
+	MiMeta,
 	MiUserNotePining,
 	MiUserProfile,
 	MutingsRepository,
@@ -100,6 +101,9 @@ export class UserEntityService implements OnModuleInit {
 		@Inject(DI.config)
 		private config: Config,
 
+		@Inject(DI.meta)
+		private meta: MiMeta,
+
 		@Inject(DI.redis)
 		private redisClient: Redis.Redis,
 
@@ -381,7 +385,11 @@ export class UserEntityService implements OnModuleInit {
 
 	@bindThis
 	public getIdenticonUrl(user: MiUser): string {
-		return `${this.config.url}/identicon/${user.username.toLowerCase()}@${user.host ?? this.config.host}`;
+		if ((user.host == null || user.host === this.config.host) && user.username.includes('.') && this.meta.iconUrl) { // ローカルのシステムアカウントの場合
+			return this.meta.iconUrl;
+		} else {
+			return `${this.config.url}/identicon/${user.username.toLowerCase()}@${user.host ?? this.config.host}`;
+		}
 	}
 
 	@bindThis
diff --git a/packages/frontend/src/pages/admin-user.vue b/packages/frontend/src/pages/admin-user.vue
index 1220b2f6aa..61bb0d47e0 100644
--- a/packages/frontend/src/pages/admin-user.vue
+++ b/packages/frontend/src/pages/admin-user.vue
@@ -22,7 +22,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 					</div>
 				</div>
 
-				<MkInfo v-if="user.host == null && user.username.startsWith('system.')">{{ i18n.ts.isSystemAccount }}</MkInfo>
+				<MkInfo v-if="user.host == null && user.username.includes('.')">{{ i18n.ts.isSystemAccount }}</MkInfo>
 
 				<FormLink v-if="user.host" :to="`/instance-info/${user.host}`">{{ i18n.ts.instanceInfo }}</FormLink>
 
diff --git a/packages/frontend/src/pages/user/home.vue b/packages/frontend/src/pages/user/home.vue
index c2a59307ee..9711ae4964 100644
--- a/packages/frontend/src/pages/user/home.vue
+++ b/packages/frontend/src/pages/user/home.vue
@@ -61,7 +61,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 							</MkA>
 						</span>
 					</div>
-					<div v-if="user.host == null && user.username.startsWith('system.')" class="isSystemAccount">
+					<div v-if="user.host == null && user.username.includes('.')" class="isSystemAccount">
 						<MkInfo>{{ i18n.ts.isSystemAccount }}</MkInfo>
 					</div>
 					<div v-if="iAmModerator" class="moderationNote">