diff --git a/packages/client/src/pizzax.ts b/packages/client/src/pizzax.ts
index 0611599a2..1ebff07fa 100644
--- a/packages/client/src/pizzax.ts
+++ b/packages/client/src/pizzax.ts
@@ -1,6 +1,7 @@
 import { onUnmounted, Ref, ref, watch } from 'vue';
 import { $i } from './account';
 import { api } from './os';
+import { get, set } from './scripts/idb-proxy';
 import { stream } from './stream';
 
 type StateDef = Record<string, {
@@ -8,119 +9,144 @@ type StateDef = Record<string, {
 	default: any;
 }>;
 
+type State<T extends StateDef> = { [K in keyof T]: T[K]['default']; };
+type ReactiveState<T extends StateDef> = { [K in keyof T]: Ref<T[K]['default']>; };
+
 type ArrayElement<A> = A extends readonly (infer T)[] ? T : never;
 
+const connection = $i ? stream.useChannel('main') : null;
+
 export class Storage<T extends StateDef> {
+	public readonly ready: PromiseLike<void>;
+
 	public readonly key: string;
-	public readonly keyForLocalStorage: string;
+	public readonly deviceStateKeyName: string;
+	public readonly deviceAccountStateKeyName: string;
+	public readonly registryCacheKeyName: string;
 
 	public readonly def: T;
 
 	// TODO: これが実装されたらreadonlyにしたい: https://github.com/microsoft/TypeScript/issues/37487
-	public readonly state: { [K in keyof T]: T[K]['default'] };
-	public readonly reactiveState: { [K in keyof T]: Ref<T[K]['default']> };
+	public readonly state = {} as State<T>;
+	public readonly reactiveState = {} as ReactiveState<T>;
 
-	private connection = stream.useChannel('main');
+	private nextIdbJob: Promise<any> = Promise.resolve();
+	private addIdbSetJob<T>(job: () => Promise<T>) {
+		const promise = this.nextIdbJob.then(job, e => {
+			console.error('Pizzax failed to save data to idb!', e);
+			return job();
+		});
+		this.nextIdbJob = promise;
+		return promise;
+	}
 
 	constructor(key: string, def: T) {
 		this.key = key;
-		this.keyForLocalStorage = 'pizzax::' + key;
+		this.deviceStateKeyName = `pizzax::${key}`;
+		this.deviceAccountStateKeyName = $i ? `pizzax::${key}::${$i.id}` : '';
+		this.registryCacheKeyName = $i ? `pizzax::${key}::cache::${$i.id}` : '';
 		this.def = def;
 
-		// TODO: indexedDBにする
-		const deviceState = JSON.parse(localStorage.getItem(this.keyForLocalStorage) || '{}');
-		const deviceAccountState = $i ? JSON.parse(localStorage.getItem(this.keyForLocalStorage + '::' + $i.id) || '{}') : {};
-		const registryCache = $i ? JSON.parse(localStorage.getItem(this.keyForLocalStorage + '::cache::' + $i.id) || '{}') : {};
-
-		const state = {};
-		const reactiveState = {};
-		for (const [k, v] of Object.entries(def)) {
-			if (v.where === 'device' && Object.prototype.hasOwnProperty.call(deviceState, k)) {
-				state[k] = deviceState[k];
-			} else if (v.where === 'account' && $i && Object.prototype.hasOwnProperty.call(registryCache, k)) {
-				state[k] = registryCache[k];
-			} else if (v.where === 'deviceAccount' && Object.prototype.hasOwnProperty.call(deviceAccountState, k)) {
-				state[k] = deviceAccountState[k];
-			} else {
-				state[k] = v.default;
-				if (_DEV_) console.log('Use default value', k, v.default);
-			}
-		}
-		for (const [k, v] of Object.entries(state)) {
-			reactiveState[k] = ref(v);
-		}
-		this.state = state as any;
-		this.reactiveState = reactiveState as any;
-
-		if ($i) {
-			// なぜかsetTimeoutしないとapi関数内でエラーになる(おそらく循環参照してることに原因がありそう)
-			setTimeout(() => {
-				api('i/registry/get-all', { scope: ['client', this.key] }).then(kvs => {
-					const cache = {};
-					for (const [k, v] of Object.entries(def)) {
-						if (v.where === 'account') {
-							if (Object.prototype.hasOwnProperty.call(kvs, k)) {
-								state[k] = kvs[k];
-								reactiveState[k].value = kvs[k];
-								cache[k] = kvs[k];
-							} else {
-								state[k] = v.default;
-								reactiveState[k].value = v.default;
-							}
-						}
-					}
-					localStorage.setItem(this.keyForLocalStorage + '::cache::' + $i.id, JSON.stringify(cache));
-				});
-			}, 1);
-			// streamingのuser storage updateイベントを監視して更新
-			this.connection.on('registryUpdated', ({ scope, key, value }: { scope: string[], key: keyof T, value: T[typeof key]['default'] }) => {
-				if (scope[1] !== this.key || this.state[key] === value) return;
-
-				this.state[key] = value;
-				this.reactiveState[key].value = value;
-
-				const cache = JSON.parse(localStorage.getItem(this.keyForLocalStorage + '::cache::' + $i.id) || '{}');
-				if (cache[key] !== value) {
-					cache[key] = value;
-					localStorage.setItem(this.keyForLocalStorage + '::cache::' + $i.id, JSON.stringify(cache));
-				}
-			});
-		}
+		this.ready = this.init();
 	}
 
-	public set<K extends keyof T>(key: K, value: T[K]['default']): void {
+	private init(): Promise<void> {
+		return new Promise(async (resolve, reject) => {
+			const deviceState: State<T> = await get(this.deviceStateKeyName);
+			const deviceAccountState = $i ? await get(this.deviceAccountStateKeyName) : {};
+			const registryCache = $i ? await get(this.registryCacheKeyName) : {};
+	
+			for (const [k, v] of Object.entries(this.def) as [keyof T, T[keyof T]][]) {
+				if (v.where === 'device' && Object.prototype.hasOwnProperty.call(deviceState, k)) {
+					this.state[k] = deviceState[k];
+				} else if (v.where === 'account' && $i && Object.prototype.hasOwnProperty.call(registryCache, k)) {
+					this.state[k] = registryCache[k];
+				} else if (v.where === 'deviceAccount' && Object.prototype.hasOwnProperty.call(deviceAccountState, k)) {
+					this.state[k] = deviceAccountState[k];
+				} else {
+					this.state[k] = v.default;
+					if (_DEV_) console.log('Use default value', k, v.default);
+				}
+			}
+			for (const [k, v] of Object.entries(this.state) as [keyof T, T[keyof T]][]) {
+				this.reactiveState[k] = ref(v);
+			}
+	
+			if ($i) {
+				// なぜかsetTimeoutしないとapi関数内でエラーになる(おそらく循環参照してることに原因がありそう)
+				setTimeout(() => {
+					api('i/registry/get-all', { scope: ['client', this.key] })
+					.then(kvs => {
+						const cache = {};
+						for (const [k, v] of Object.entries(this.def)) {
+							if (v.where === 'account') {
+								if (Object.prototype.hasOwnProperty.call(kvs, k)) {
+									this.state[k as keyof T] = kvs[k];
+									this.reactiveState[k as keyof T].value = kvs[k as string];
+									cache[k] = kvs[k];
+								} else {
+									this.state[k as keyof T] = v.default;
+									this.reactiveState[k].value = v.default;
+								}
+							}
+						}
+
+						return set(this.registryCacheKeyName, cache);
+					})
+					.then(() => resolve());
+				}, 1);
+				// streamingのuser storage updateイベントを監視して更新
+				connection?.on('registryUpdated', async ({ scope, key, value }: { scope: string[], key: keyof T, value: T[typeof key]['default'] }) => {
+					if (scope[1] !== this.key || this.state[key] === value) return;
+	
+					this.state[key] = value;
+					this.reactiveState[key].value = value;
+	
+					const cache = await get(this.registryCacheKeyName);
+					if (cache[key] !== value) {
+						cache[key] = value;
+						await set(this.registryCacheKeyName, cache);
+					}
+				});
+			}
+		});
+	}
+
+	public set<K extends keyof T>(key: K, value: T[K]['default']): Promise<void> {
 		if (_DEV_) console.log('set', key, value);
 
 		this.state[key] = value;
 		this.reactiveState[key].value = value;
 
-		switch (this.def[key].where) {
-			case 'device': {
-				const deviceState = JSON.parse(localStorage.getItem(this.keyForLocalStorage) || '{}');
-				deviceState[key] = value;
-				localStorage.setItem(this.keyForLocalStorage, JSON.stringify(deviceState));
-				break;
+		return this.addIdbSetJob(async () => {
+			switch (this.def[key].where) {
+				case 'device': {
+					const deviceState = await get(this.deviceStateKeyName) || {};
+					deviceState[key] = value;
+					await set(this.deviceStateKeyName, deviceState);
+					break;
+				}
+				case 'deviceAccount': {
+					if ($i == null) break;
+					const deviceAccountState = await get(this.deviceAccountStateKeyName) || {};
+					deviceAccountState[key] = value;
+					await set(this.deviceAccountStateKeyName, deviceAccountState);
+					break;
+				}
+				case 'account': {
+					if ($i == null) break;
+					const cache = await get(this.registryCacheKeyName) || {};
+					cache[key] = value;
+					await set(this.registryCacheKeyName, cache);
+					await api('i/registry/set', {
+						scope: ['client', this.key],
+						key: key,
+						value: value
+					});
+					break;
+				}
 			}
-			case 'deviceAccount': {
-				if ($i == null) break;
-				const deviceAccountState = JSON.parse(localStorage.getItem(this.keyForLocalStorage + '::' + $i.id) || '{}');
-				deviceAccountState[key] = value;
-				localStorage.setItem(this.keyForLocalStorage + '::' + $i.id, JSON.stringify(deviceAccountState));
-				break;
-			}
-			case 'account': {
-				if ($i == null) break;
-				const cache = JSON.parse(localStorage.getItem(this.keyForLocalStorage + '::cache::' + $i.id) || '{}');
-				cache[key] = value;
-				localStorage.setItem(this.keyForLocalStorage + '::cache::' + $i.id, JSON.stringify(cache));
-				api('i/registry/set', {
-					scope: ['client', this.key],
-					key: key,
-					value: value
-				});
-				break;
-			}
-		}
+		});
 	}
 
 	public push<K extends keyof T>(key: K, value: ArrayElement<T[K]['default']>): void {