diff --git a/locales/ja-JP.yml b/locales/ja-JP.yml
index bd6cee0272..1d05755629 100644
--- a/locales/ja-JP.yml
+++ b/locales/ja-JP.yml
@@ -906,6 +906,8 @@ pushNotificationAlreadySubscribed: "プッシュ通知は有効です"
 pushNotificationNotSupported: "ブラウザかインスタンスがプッシュ通知に非対応"
 sendPushNotificationReadMessage: "通知やメッセージが既読になったらプッシュ通知を削除する"
 sendPushNotificationReadMessageCaption: "「{emptyPushNotificationMessage}」という通知が一瞬表示されるようになります。端末の電池消費量が増加する可能性があります。"
+windowMaximize: "最大化"
+windowRestore: "元に戻す"
 
 _sensitiveMediaDetection:
   description: "機械学習を使って自動でセンシティブなメディアを検出し、モデレーションに役立てることができます。サーバーの負荷が少し増えます。"
diff --git a/packages/client/src/components/MkUrlPreview.vue b/packages/client/src/components/MkUrlPreview.vue
index 4f75d31db4..9ef6efa1e5 100644
--- a/packages/client/src/components/MkUrlPreview.vue
+++ b/packages/client/src/components/MkUrlPreview.vue
@@ -82,7 +82,7 @@ if (requestUrl.hostname === 'music.youtube.com' && requestUrl.pathname.match('^/
 	requestUrl.hostname = 'www.youtube.com';
 }
 
-const requestLang = (lang || 'ja-JP').replace('ja-KS', 'ja-JP');
+const requestLang = (lang ?? 'ja-JP').replace('ja-KS', 'ja-JP');
 
 requestUrl.hash = '';
 
diff --git a/packages/client/src/components/MkWindow.vue b/packages/client/src/components/MkWindow.vue
index 13c4e90f3e..d9c0035a86 100644
--- a/packages/client/src/components/MkWindow.vue
+++ b/packages/client/src/components/MkWindow.vue
@@ -11,9 +11,9 @@
 				</span>
 				<span class="right">
 					<button v-for="button in buttonsRight" v-tooltip="button.title" class="button _button" :class="{ highlighted: button.highlighted }" @click="button.onClick"><i :class="button.icon"></i></button>
-					<button v-if="canResize && maximized" class="button _button" @click="unMaximize()"><i class="ti ti-app-window"></i></button>
-					<button v-else-if="canResize && !maximized" class="button _button" @click="maximize()"><i class="ti ti-arrows-maximize"></i></button>
-					<button v-if="closeButton" class="button _button" @click="close()"><i class="ti ti-x"></i></button>
+					<button v-if="canResize && maximized" v-tooltip="i18n.ts.windowRestore" class="button _button" @click="unMaximize()"><i class="ti ti-app-window"></i></button>
+					<button v-else-if="canResize && !maximized" v-tooltip="i18n.ts.windowMaximize" class="button _button" @click="maximize()"><i class="ti ti-arrows-maximize"></i></button>
+					<button v-if="closeButton" v-tooltip="i18n.ts.close" class="button _button" @click="close()"><i class="ti ti-x"></i></button>
 				</span>
 			</div>
 			<div class="body">
@@ -39,6 +39,7 @@ import { onBeforeUnmount, onMounted, provide } from 'vue';
 import contains from '@/scripts/contains';
 import * as os from '@/os';
 import { MenuItem } from '@/types/menu';
+import { i18n } from '@/i18n';
 
 const minHeight = 50;
 const minWidth = 250;
@@ -431,10 +432,10 @@ defineExpose({
 		border-radius: var(--radius);
 
 		> .header {
-			--height: 42px;
+			--height: 39px;
 
 			&.mini {
-				--height: 38px;
+				--height: 32px;
 			}
 
 			display: flex;
diff --git a/packages/client/src/components/MkYoutubePlayer.vue b/packages/client/src/components/MkYoutubePlayer.vue
index 815dc82a27..8cd481a39c 100644
--- a/packages/client/src/components/MkYoutubePlayer.vue
+++ b/packages/client/src/components/MkYoutubePlayer.vue
@@ -1,8 +1,8 @@
 <template>
 <XWindow :initial-width="640" :initial-height="402" :can-resize="true" :close-button="true">
 	<template #header>
-		<i class="icon fa-brands fa-youtube" style="margin-right: 0.5em;"></i>
-		<span>{{ title ?? 'YouTube Player' }}</span>
+		<i class="icon ti ti-brand-youtube" style="margin-right: 0.5em;"></i>
+		<span>{{ title ?? 'YouTube' }}</span>
 	</template>
 
 	<div class="poamfof">