diff --git a/CHANGELOG.md b/CHANGELOG.md
index b713d617f3..5dbde8ec5c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,7 +4,8 @@
 -
 
 ### Client
--
+- 2025.4.0 以前の設定情報の移行処理が削除されました
+	- 2025.4.0 から直接 2026.6.0 以上にアップデートする場合は設定が移行されませんので注意してください。移行したい場合は一度 2026.5.1 を経由してください。
 
 ### Server
 -
diff --git a/locales/ja-JP.yml b/locales/ja-JP.yml
index 5512deb972..19636396ad 100644
--- a/locales/ja-JP.yml
+++ b/locales/ja-JP.yml
@@ -1358,14 +1358,11 @@ information: "情報"
 chat: "チャット"
 directMessage: "ダイレクトメッセージ"
 directMessage_short: "メッセージ"
-migrateOldSettings: "旧設定情報を移行"
-migrateOldSettings_description: "通常これは自動で行われていますが、何らかの理由により上手く移行されなかった場合は手動で移行処理をトリガーできます。現在の設定情報は上書きされます。"
 compress: "圧縮"
 right: "右"
 bottom: "下"
 top: "上"
 embed: "埋め込み"
-settingsMigrating: "設定を移行しています。しばらくお待ちください... (後ほど、設定→その他→旧設定情報を移行 で手動で移行することもできます)"
 readonly: "読み取り専用"
 goToDeck: "デッキへ戻る"
 federationJobs: "連合ジョブ"
diff --git a/packages/frontend/src/boot/main-boot.ts b/packages/frontend/src/boot/main-boot.ts
index 3d4ecbf75b..5a5c91cf90 100644
--- a/packages/frontend/src/boot/main-boot.ts
+++ b/packages/frontend/src/boot/main-boot.ts
@@ -27,7 +27,6 @@ import { makeHotkey } from '@/utility/hotkey.js';
 import { addCustomEmoji, removeCustomEmojis, updateCustomEmojis } from '@/custom-emojis.js';
 import { prefer } from '@/preferences.js';
 import { updateCurrentAccountPartial } from '@/accounts.js';
-import { migrateOldSettings } from '@/pref-migrate.js';
 import { unisonReload } from '@/utility/unison-reload.js';
 import { isBirthday } from '@/utility/is-birthday.js';
 
@@ -69,14 +68,6 @@ export async function mainBoot() {
 		const { dispose } = popup(defineAsyncComponent(() => import('@/components/MkUpdated.vue')), {}, {
 			closed: () => dispose(),
 		});
-
-		// prefereces migration
-		// TODO: そのうち消す
-		if (lastVersion && (compareVersions('2025.3.2-alpha.0', lastVersion) === 1)) {
-			console.log('Preferences migration');
-
-			migrateOldSettings();
-		}
 	}
 
 	try {
diff --git a/packages/frontend/src/pages/settings/other.vue b/packages/frontend/src/pages/settings/other.vue
index 4facc696a4..6ab645ed1c 100644
--- a/packages/frontend/src/pages/settings/other.vue
+++ b/packages/frontend/src/pages/settings/other.vue
@@ -145,11 +145,6 @@ SPDX-License-Identifier: AGPL-3.0-only
 		<MkButton v-if="storagePersistenceSupported && !storagePersisted" @click="enableStoragePersistence">{{ i18n.ts._settings.settingsPersistence_title }}</MkButton>
 
 		<MkButton @click="forceCloudBackup">{{ i18n.ts._preferencesBackup.forceBackup }}</MkButton>
-
-		<FormSlot>
-			<MkButton danger @click="migrate"><i class="ti ti-refresh"></i> {{ i18n.ts.migrateOldSettings }}</MkButton>
-			<template #caption>{{ i18n.ts.migrateOldSettings_description }}</template>
-		</FormSlot>
 	</div>
 </SearchMarker>
 </template>
@@ -173,7 +168,6 @@ import FormSection from '@/components/form/section.vue';
 import { prefer } from '@/preferences.js';
 import MkRolePreview from '@/components/MkRolePreview.vue';
 import { signout } from '@/signout.js';
-import { migrateOldSettings } from '@/pref-migrate.js';
 import { hideAllTips as _hideAllTips, resetAllTips as _resetAllTips } from '@/tips.js';
 import { suggestReload } from '@/utility/reload-suggest.js';
 import { cloudBackup } from '@/preferences/utility.js';
@@ -219,10 +213,6 @@ async function deleteAccount() {
 	await signout();
 }
 
-function migrate() {
-	migrateOldSettings();
-}
-
 function resetAllTips() {
 	_resetAllTips();
 	os.success();
diff --git a/packages/frontend/src/pref-migrate.ts b/packages/frontend/src/pref-migrate.ts
deleted file mode 100644
index bf86f6954e..0000000000
--- a/packages/frontend/src/pref-migrate.ts
+++ /dev/null
@@ -1,141 +0,0 @@
-/*
- * SPDX-FileCopyrightText: syuilo and misskey-project
- * SPDX-License-Identifier: AGPL-3.0-only
- */
-
-import type { DeckProfile } from '@/deck.js';
-import { genId } from '@/utility/id.js';
-import { store } from '@/store.js';
-import { prefer } from '@/preferences.js';
-import { misskeyApi } from '@/utility/misskey-api.js';
-import { deckStore } from '@/ui/deck/deck-store.js';
-import { unisonReload } from '@/utility/unison-reload.js';
-import * as os from '@/os.js';
-import { i18n } from '@/i18n.js';
-import type { SoundStore } from '@/preferences/def.js';
-
-// TODO: そのうち消す
-export function migrateOldSettings() {
-	os.waiting({ text: i18n.ts.settingsMigrating });
-
-	store.loaded.then(async () => {
-		misskeyApi('i/registry/get', { scope: ['client'], key: 'themes' }).catch(() => []).then((themes: any) => {
-			if (themes.length > 0) {
-				prefer.commit('themes', themes);
-			}
-		});
-
-		prefer.commit('deck.profile', deckStore.s.profile);
-		misskeyApi('i/registry/keys', {
-			scope: ['client', 'deck', 'profiles'],
-		}).then(async keys => {
-			const profiles: DeckProfile[] = [];
-			for (const key of keys) {
-				const deck = await misskeyApi('i/registry/get', {
-					scope: ['client', 'deck', 'profiles'],
-					key: key,
-				});
-				profiles.push({
-					id: genId(),
-					name: key,
-					columns: deck.columns,
-					layout: deck.layout,
-				});
-			}
-			prefer.commit('deck.profiles', profiles);
-		});
-
-		prefer.commit('emojiPalettes', [{
-			id: 'reactions',
-			name: '',
-			emojis: store.s.reactions,
-		}, {
-			id: 'pinnedEmojis',
-			name: '',
-			emojis: store.s.pinnedEmojis,
-		}]);
-		prefer.commit('emojiPaletteForMain', 'pinnedEmojis');
-		prefer.commit('emojiPaletteForReaction', 'reactions');
-		prefer.commit('overridedDeviceKind', store.s.overridedDeviceKind);
-		prefer.commit('widgets', store.s.widgets);
-		prefer.commit('keepCw', store.s.keepCw);
-		prefer.commit('collapseRenotes', store.s.collapseRenotes);
-		prefer.commit('rememberNoteVisibility', store.s.rememberNoteVisibility);
-		prefer.commit('uploadFolder', store.s.uploadFolder);
-		prefer.commit('menu', [...store.s.menu, 'chat']);
-		prefer.commit('statusbars', store.s.statusbars);
-		prefer.commit('pinnedUserLists', store.s.pinnedUserLists);
-		prefer.commit('serverDisconnectedBehavior', store.s.serverDisconnectedBehavior);
-		prefer.commit('nsfw', store.s.nsfw);
-		prefer.commit('highlightSensitiveMedia', store.s.highlightSensitiveMedia);
-		prefer.commit('animation', store.s.animation);
-		prefer.commit('animatedMfm', store.s.animatedMfm);
-		prefer.commit('advancedMfm', store.s.advancedMfm);
-		prefer.commit('showReactionsCount', store.s.showReactionsCount);
-		prefer.commit('enableQuickAddMfmFunction', store.s.enableQuickAddMfmFunction);
-		prefer.commit('loadRawImages', store.s.loadRawImages);
-		prefer.commit('imageNewTab', store.s.imageNewTab);
-		prefer.commit('disableShowingAnimatedImages', store.s.disableShowingAnimatedImages);
-		prefer.commit('emojiStyle', store.s.emojiStyle);
-		prefer.commit('menuStyle', store.s.menuStyle);
-		prefer.commit('useBlurEffectForModal', store.s.useBlurEffectForModal);
-		prefer.commit('useBlurEffect', store.s.useBlurEffect);
-		prefer.commit('showFixedPostForm', store.s.showFixedPostForm);
-		prefer.commit('showFixedPostFormInChannel', store.s.showFixedPostFormInChannel);
-		prefer.commit('enableInfiniteScroll', store.s.enableInfiniteScroll);
-		prefer.commit('useReactionPickerForContextMenu', store.s.useReactionPickerForContextMenu);
-		prefer.commit('instanceTicker', store.s.instanceTicker);
-		prefer.commit('emojiPickerScale', store.s.emojiPickerScale);
-		prefer.commit('emojiPickerWidth', store.s.emojiPickerWidth);
-		prefer.commit('emojiPickerHeight', store.s.emojiPickerHeight);
-		prefer.commit('emojiPickerStyle', store.s.emojiPickerStyle);
-		prefer.commit('reportError', store.s.reportError);
-		prefer.commit('squareAvatars', store.s.squareAvatars);
-		prefer.commit('showAvatarDecorations', store.s.showAvatarDecorations);
-		prefer.commit('numberOfPageCache', store.s.numberOfPageCache);
-		prefer.commit('showNoteActionsOnlyHover', store.s.showNoteActionsOnlyHover);
-		prefer.commit('showClipButtonInNoteFooter', store.s.showClipButtonInNoteFooter);
-		prefer.commit('reactionsDisplaySize', store.s.reactionsDisplaySize);
-		prefer.commit('limitWidthOfReaction', store.s.limitWidthOfReaction);
-		prefer.commit('forceShowAds', store.s.forceShowAds);
-		prefer.commit('aiChanMode', store.s.aiChanMode);
-		prefer.commit('devMode', store.s.devMode);
-		prefer.commit('mediaListWithOneImageAppearance', store.s.mediaListWithOneImageAppearance);
-		prefer.commit('notificationPosition', store.s.notificationPosition);
-		prefer.commit('notificationStackAxis', store.s.notificationStackAxis);
-		prefer.commit('enableCondensedLine', store.s.enableCondensedLine);
-		prefer.commit('keepScreenOn', store.s.keepScreenOn);
-		prefer.commit('useGroupedNotifications', store.s.useGroupedNotifications);
-		prefer.commit('dataSaver', {
-			...prefer.s.dataSaver,
-			media: store.s.dataSaver.media,
-			avatar: store.s.dataSaver.avatar,
-			urlPreviewThumbnail: store.s.dataSaver.urlPreview,
-			code: store.s.dataSaver.code,
-		});
-		prefer.commit('enableSeasonalScreenEffect', store.s.enableSeasonalScreenEffect);
-		prefer.commit('enableHorizontalSwipe', store.s.enableHorizontalSwipe);
-		prefer.commit('useNativeUiForVideoAudioPlayer', store.s.useNativeUIForVideoAudioPlayer);
-		prefer.commit('keepOriginalFilename', store.s.keepOriginalFilename);
-		prefer.commit('alwaysConfirmFollow', store.s.alwaysConfirmFollow);
-		prefer.commit('confirmWhenRevealingSensitiveMedia', store.s.confirmWhenRevealingSensitiveMedia);
-		prefer.commit('contextMenu', store.s.contextMenu);
-		prefer.commit('skipNoteRender', store.s.skipNoteRender);
-		prefer.commit('showSoftWordMutedWord', store.s.showSoftWordMutedWord);
-		prefer.commit('confirmOnReact', store.s.confirmOnReact);
-		prefer.commit('defaultFollowWithReplies', store.s.defaultWithReplies);
-		prefer.commit('sound.masterVolume', store.s.sound_masterVolume);
-		prefer.commit('sound.notUseSound', store.s.sound_notUseSound);
-		prefer.commit('sound.useSoundOnlyWhenActive', store.s.sound_useSoundOnlyWhenActive);
-		prefer.commit('sound.on.note', store.s.sound_note as SoundStore);
-		prefer.commit('sound.on.noteMy', store.s.sound_noteMy as SoundStore);
-		prefer.commit('sound.on.notification', store.s.sound_notification as SoundStore);
-		prefer.commit('sound.on.reaction', store.s.sound_reaction as SoundStore);
-		prefer.commit('defaultNoteVisibility', store.s.defaultNoteVisibility);
-		prefer.commit('defaultNoteLocalOnly', store.s.defaultNoteLocalOnly);
-
-		window.setTimeout(() => {
-			unisonReload();
-		}, 10000);
-	});
-}
diff --git a/packages/frontend/src/store.ts b/packages/frontend/src/store.ts
index e7cdc98415..7017725e30 100644
--- a/packages/frontend/src/store.ts
+++ b/packages/frontend/src/store.ts
@@ -118,352 +118,6 @@ export const store = markRaw(new Pizzax('base', {
 		where: 'device',
 		default: true,
 	},
-
-	//#region TODO: そのうち消す (preferに移行済み)
-	defaultWithReplies: {
-		where: 'account',
-		default: false,
-	},
-	reactions: {
-		where: 'account',
-		default: ['👍', '❤️', '😆', '🤔', '😮', '🎉', '💢', '😥', '😇', '🍮'],
-	},
-	pinnedEmojis: {
-		where: 'account',
-		default: [],
-	},
-	widgets: {
-		where: 'account',
-		default: [] as {
-			name: string;
-			id: string;
-			place: string | null;
-			data: Record<string, any>;
-		}[],
-	},
-	overridedDeviceKind: {
-		where: 'device',
-		default: null as DeviceKind | null,
-	},
-	defaultSideView: {
-		where: 'device',
-		default: false,
-	},
-	defaultNoteVisibility: {
-		where: 'account',
-		default: 'public' as (typeof Misskey.noteVisibilities)[number],
-	},
-	defaultNoteLocalOnly: {
-		where: 'account',
-		default: false,
-	},
-	keepCw: {
-		where: 'account',
-		default: true,
-	},
-	collapseRenotes: {
-		where: 'account',
-		default: true,
-	},
-	rememberNoteVisibility: {
-		where: 'account',
-		default: false,
-	},
-	uploadFolder: {
-		where: 'account',
-		default: null as string | null,
-	},
-	keepOriginalUploading: {
-		where: 'account',
-		default: false,
-	},
-	menu: {
-		where: 'deviceAccount',
-		default: [
-			'notifications',
-			'clips',
-			'drive',
-			'followRequests',
-			'-',
-			'explore',
-			'announcements',
-			'search',
-			'-',
-			'ui',
-		],
-	},
-	statusbars: {
-		where: 'deviceAccount',
-		default: [] as {
-			name: string;
-			id: string;
-			type: string;
-			size: 'verySmall' | 'small' | 'medium' | 'large' | 'veryLarge';
-			black: boolean;
-			props: Record<string, any>;
-		}[],
-	},
-	pinnedUserLists: {
-		where: 'deviceAccount',
-		default: [] as Misskey.entities.UserList[],
-	},
-	serverDisconnectedBehavior: {
-		where: 'device',
-		default: 'quiet' as 'quiet' | 'reload' | 'dialog',
-	},
-	nsfw: {
-		where: 'device',
-		default: 'respect' as 'respect' | 'force' | 'ignore',
-	},
-	highlightSensitiveMedia: {
-		where: 'device',
-		default: false,
-	},
-	animation: {
-		where: 'device',
-		default: !prefersReducedMotion,
-	},
-	animatedMfm: {
-		where: 'device',
-		default: !prefersReducedMotion,
-	},
-	advancedMfm: {
-		where: 'device',
-		default: true,
-	},
-	showReactionsCount: {
-		where: 'device',
-		default: false,
-	},
-	enableQuickAddMfmFunction: {
-		where: 'device',
-		default: false,
-	},
-	loadRawImages: {
-		where: 'device',
-		default: false,
-	},
-	imageNewTab: {
-		where: 'device',
-		default: false,
-	},
-	disableShowingAnimatedImages: {
-		where: 'device',
-		default: prefersReducedMotion,
-	},
-	emojiStyle: {
-		where: 'device',
-		default: 'twemoji' as 'twemoji' | 'fluentEmoji' | 'native',
-	},
-	menuStyle: {
-		where: 'device',
-		default: 'auto' as 'auto' | 'popup' | 'drawer',
-	},
-	useBlurEffectForModal: {
-		where: 'device',
-		default: DEFAULT_DEVICE_KIND === 'desktop',
-	},
-	useBlurEffect: {
-		where: 'device',
-		default: DEFAULT_DEVICE_KIND === 'desktop',
-	},
-	showFixedPostForm: {
-		where: 'device',
-		default: false,
-	},
-	showFixedPostFormInChannel: {
-		where: 'device',
-		default: false,
-	},
-	enableInfiniteScroll: {
-		where: 'device',
-		default: true,
-	},
-	useReactionPickerForContextMenu: {
-		where: 'device',
-		default: false,
-	},
-	showGapBetweenNotesInTimeline: {
-		where: 'device',
-		default: false,
-	},
-	instanceTicker: {
-		where: 'device',
-		default: 'remote' as 'none' | 'remote' | 'always',
-	},
-	emojiPickerScale: {
-		where: 'device',
-		default: 1,
-	},
-	emojiPickerWidth: {
-		where: 'device',
-		default: 1,
-	},
-	emojiPickerHeight: {
-		where: 'device',
-		default: 2,
-	},
-	emojiPickerStyle: {
-		where: 'device',
-		default: 'auto' as 'auto' | 'popup' | 'drawer',
-	},
-	reportError: {
-		where: 'device',
-		default: false,
-	},
-	squareAvatars: {
-		where: 'device',
-		default: false,
-	},
-	showAvatarDecorations: {
-		where: 'device',
-		default: true,
-	},
-	numberOfPageCache: {
-		where: 'device',
-		default: 3,
-	},
-	showNoteActionsOnlyHover: {
-		where: 'device',
-		default: false,
-	},
-	showClipButtonInNoteFooter: {
-		where: 'device',
-		default: false,
-	},
-	reactionsDisplaySize: {
-		where: 'device',
-		default: 'medium' as 'small' | 'medium' | 'large',
-	},
-	limitWidthOfReaction: {
-		where: 'device',
-		default: true,
-	},
-	forceShowAds: {
-		where: 'device',
-		default: false,
-	},
-	aiChanMode: {
-		where: 'device',
-		default: false,
-	},
-	devMode: {
-		where: 'device',
-		default: false,
-	},
-	mediaListWithOneImageAppearance: {
-		where: 'device',
-		default: 'expand' as 'expand' | '16_9' | '1_1' | '2_3',
-	},
-	notificationPosition: {
-		where: 'device',
-		default: 'rightBottom' as 'leftTop' | 'leftBottom' | 'rightTop' | 'rightBottom',
-	},
-	notificationStackAxis: {
-		where: 'device',
-		default: 'horizontal' as 'vertical' | 'horizontal',
-	},
-	enableCondensedLine: {
-		where: 'device',
-		default: true,
-	},
-	keepScreenOn: {
-		where: 'device',
-		default: false,
-	},
-	useGroupedNotifications: {
-		where: 'device',
-		default: true,
-	},
-	dataSaver: {
-		where: 'device',
-		default: {
-			media: false,
-			avatar: false,
-			urlPreview: false,
-			code: false,
-		},
-	},
-	enableSeasonalScreenEffect: {
-		where: 'device',
-		default: false,
-	},
-	enableHorizontalSwipe: {
-		where: 'device',
-		default: true,
-	},
-	useNativeUIForVideoAudioPlayer: {
-		where: 'device',
-		default: false,
-	},
-	keepOriginalFilename: {
-		where: 'device',
-		default: true,
-	},
-	alwaysConfirmFollow: {
-		where: 'device',
-		default: true,
-	},
-	confirmWhenRevealingSensitiveMedia: {
-		where: 'device',
-		default: false,
-	},
-	contextMenu: {
-		where: 'device',
-		default: 'app' as 'app' | 'appWithShift' | 'native',
-	},
-	skipNoteRender: {
-		where: 'device',
-		default: true,
-	},
-	showSoftWordMutedWord: {
-		where: 'device',
-		default: false,
-	},
-	confirmOnReact: {
-		where: 'device',
-		default: false,
-	},
-	hemisphere: {
-		where: 'device',
-		default: hemisphere as 'N' | 'S',
-	},
-	sound_masterVolume: {
-		where: 'device',
-		default: 0.3,
-	},
-	sound_notUseSound: {
-		where: 'device',
-		default: false,
-	},
-	sound_useSoundOnlyWhenActive: {
-		where: 'device',
-		default: false,
-	},
-	sound_note: {
-		where: 'device',
-		default: { type: 'syuilo/n-aec', volume: 1 },
-	},
-	sound_noteMy: {
-		where: 'device',
-		default: { type: 'syuilo/n-cea-4va', volume: 1 },
-	},
-	sound_notification: {
-		where: 'device',
-		default: { type: 'syuilo/n-ea', volume: 1 },
-	},
-	sound_reaction: {
-		where: 'device',
-		default: { type: 'syuilo/bubble2', volume: 1 },
-	},
-	dropAndFusion: {
-		where: 'device',
-		default: {
-			bgmVolume: 0.25,
-			sfxVolume: 1,
-		},
-	},
-	//#endregion
 }));
 
 // TODO: 他のタブと永続化されたstateを同期
diff --git a/packages/i18n/src/autogen/locale.ts b/packages/i18n/src/autogen/locale.ts
index 07e9a3afc1..7a4d46abf5 100644
--- a/packages/i18n/src/autogen/locale.ts
+++ b/packages/i18n/src/autogen/locale.ts
@@ -5444,14 +5444,6 @@ export interface Locale extends ILocale {
      * メッセージ
      */
     "directMessage_short": string;
-    /**
-     * 旧設定情報を移行
-     */
-    "migrateOldSettings": string;
-    /**
-     * 通常これは自動で行われていますが、何らかの理由により上手く移行されなかった場合は手動で移行処理をトリガーできます。現在の設定情報は上書きされます。
-     */
-    "migrateOldSettings_description": string;
     /**
      * 圧縮
      */
@@ -5472,10 +5464,6 @@ export interface Locale extends ILocale {
      * 埋め込み
      */
     "embed": string;
-    /**
-     * 設定を移行しています。しばらくお待ちください... (後ほど、設定→その他→旧設定情報を移行 で手動で移行することもできます)
-     */
-    "settingsMigrating": string;
     /**
      * 読み取り専用
      */