diff --git a/locales/ja-JP.yml b/locales/ja-JP.yml
index bbbb037a8e..7788a04dc3 100644
--- a/locales/ja-JP.yml
+++ b/locales/ja-JP.yml
@@ -854,6 +854,7 @@ noEmailServerWarning: "メールサーバーの設定がされていません。
 thereIsUnresolvedAbuseReportWarning: "未対応の通報があります。"
 recommended: "推奨"
 check: "チェック"
+isSystemAccount: "システムにより自動で作成・管理されているアカウントです。"
 
 _emailUnavailable:
   used: "既に使用されています"
diff --git a/packages/client/src/pages/admin-file.vue b/packages/client/src/pages/admin-file.vue
index 67ebdd4678..402e9502d2 100644
--- a/packages/client/src/pages/admin-file.vue
+++ b/packages/client/src/pages/admin-file.vue
@@ -28,7 +28,7 @@
 					<template #value><span class="_monospace"><MkTime :time="file.createdAt" mode="detail" style="display: block;"/></span></template>
 				</MkKeyValue>
 			</div>
-			<MkA class="user" :to="`/user-info/${file.user.id}`">
+			<MkA v-if="file.user" class="user" :to="`/user-info/${file.user.id}`">
 				<MkUserCardMini :user="file.user"/>
 			</MkA>
 			<div class="_formBlock">
diff --git a/packages/client/src/pages/user-info.vue b/packages/client/src/pages/user-info.vue
index b4c4aedfcd..86c1be8d06 100644
--- a/packages/client/src/pages/user-info.vue
+++ b/packages/client/src/pages/user-info.vue
@@ -12,6 +12,8 @@
 					</div>
 				</div>
 
+				<MkInfo v-if="user.username.includes('.')" class="_formBlock">{{ i18n.ts.isSystemAccount }}</MkInfo>
+
 				<div v-if="user.url" class="_formLinksGrid _formBlock">
 					<FormLink :to="userPage(user)">Profile</FormLink>
 					<FormLink :to="user.url" :external="true">Profile (remote)</FormLink>