diff --git a/ext/bg/js/search-main.js b/ext/bg/js/search-main.js
index 1075d46e..6e092fbc 100644
--- a/ext/bg/js/search-main.js
+++ b/ext/bg/js/search-main.js
@@ -31,7 +31,7 @@ async function injectSearchFrontend() {
         '/fg/js/frontend-api-receiver.js',
         '/fg/js/frame-offset-forwarder.js',
         '/fg/js/popup.js',
-        '/fg/js/popup-proxy-host.js',
+        '/fg/js/popup-factory.js',
         '/fg/js/frontend.js',
         '/fg/js/content-script-main.js'
     ]);
diff --git a/ext/bg/js/settings/popup-preview-frame.js b/ext/bg/js/settings/popup-preview-frame.js
index c7b0c218..8901a0c4 100644
--- a/ext/bg/js/settings/popup-preview-frame.js
+++ b/ext/bg/js/settings/popup-preview-frame.js
@@ -18,8 +18,9 @@
 /* global
  * Frontend
  * Popup
- * PopupProxyHost
+ * PopupFactory
  * TextSourceRange
+ * apiFrameInformationGet
  * apiOptionsGet
  */
 
@@ -56,10 +57,12 @@ class SettingsPopupPreview {
         window.apiOptionsGet = this.apiOptionsGet.bind(this);
 
         // Overwrite frontend
-        const popupHost = new PopupProxyHost();
-        await popupHost.prepare();
+        const {frameId} = await apiFrameInformationGet();
 
-        this.popup = popupHost.getOrCreatePopup();
+        const popupFactory = new PopupFactory(frameId);
+        await popupFactory.prepare();
+
+        this.popup = popupFactory.getOrCreatePopup();
         this.popup.setChildrenSupported(false);
 
         this.popupSetCustomOuterCssOld = this.popup.setCustomOuterCss;
diff --git a/ext/bg/settings-popup-preview.html b/ext/bg/settings-popup-preview.html
index a332fb22..3d7f6455 100644
--- a/ext/bg/settings-popup-preview.html
+++ b/ext/bg/settings-popup-preview.html
@@ -127,7 +127,7 @@
         <script src="/fg/js/frontend-api-receiver.js"></script>
         <script src="/fg/js/popup.js"></script>
         <script src="/fg/js/source.js"></script>
-        <script src="/fg/js/popup-proxy-host.js"></script>
+        <script src="/fg/js/popup-factory.js"></script>
         <script src="/fg/js/frontend.js"></script>
         <script src="/bg/js/settings/popup-preview-frame.js"></script>
 
diff --git a/ext/fg/js/content-script-main.js b/ext/fg/js/content-script-main.js
index 277e6567..3afc9648 100644
--- a/ext/fg/js/content-script-main.js
+++ b/ext/fg/js/content-script-main.js
@@ -19,10 +19,11 @@
  * DOM
  * FrameOffsetForwarder
  * Frontend
+ * PopupFactory
  * PopupProxy
- * PopupProxyHost
  * apiBroadcastTab
  * apiForwardLogsToBackend
+ * apiFrameInformationGet
  * apiOptionsGet
  */
 
@@ -47,10 +48,17 @@ async function createIframePopupProxy(frameOffsetForwarder, setDisabled) {
 }
 
 async function getOrCreatePopup(depth) {
-    const popupHost = new PopupProxyHost();
-    await popupHost.prepare();
+    const {frameId} = await apiFrameInformationGet();
+    if (typeof frameId !== 'number') {
+        const error = new Error('Failed to get frameId');
+        yomichan.logError(error);
+        throw error;
+    }
 
-    const popup = popupHost.getOrCreatePopup(null, null, depth);
+    const popupFactory = new PopupFactory(frameId);
+    await popupFactory.prepare();
+
+    const popup = popupFactory.getOrCreatePopup(null, null, depth);
 
     return popup;
 }
@@ -89,20 +97,20 @@ async function createPopupProxy(depth, id, parentFrameId) {
     };
 
     let urlUpdatedAt = 0;
-    let proxyHostUrlCached = url;
-    const getProxyHostUrl = async () => {
+    let popupProxyUrlCached = url;
+    const getPopupProxyUrl = async () => {
         const now = Date.now();
         if (popups.proxy !== null && now - urlUpdatedAt > 500) {
-            proxyHostUrlCached = await popups.proxy.getHostUrl();
+            popupProxyUrlCached = await popups.proxy.getUrl();
             urlUpdatedAt = now;
         }
-        return proxyHostUrlCached;
+        return popupProxyUrlCached;
     };
 
     const applyOptions = async () => {
         const optionsContext = {
             depth: isSearchPage ? 0 : depth,
-            url: proxy ? await getProxyHostUrl() : window.location.href
+            url: proxy ? await getPopupProxyUrl() : window.location.href
         };
         const options = await apiOptionsGet(optionsContext);
 
@@ -124,7 +132,7 @@ async function createPopupProxy(depth, id, parentFrameId) {
         }
 
         if (frontend === null) {
-            const getUrl = proxy ? getProxyHostUrl : null;
+            const getUrl = proxy ? getPopupProxyUrl : null;
             frontend = new Frontend(popup, getUrl);
             frontendPreparePromise = frontend.prepare();
             await frontendPreparePromise;
diff --git a/ext/fg/js/frontend-api-receiver.js b/ext/fg/js/frontend-api-receiver.js
index c5bb58af..3fa9e8b6 100644
--- a/ext/fg/js/frontend-api-receiver.js
+++ b/ext/fg/js/frontend-api-receiver.js
@@ -17,9 +17,9 @@
 
 
 class FrontendApiReceiver {
-    constructor(source='', handlers=new Map()) {
+    constructor(source, messageHandlers) {
         this._source = source;
-        this._handlers = handlers;
+        this._messageHandlers = messageHandlers;
     }
 
     prepare() {
@@ -35,14 +35,29 @@ class FrontendApiReceiver {
     _onMessage(port, {id, action, params, target, senderId}) {
         if (target !== this._source) { return; }
 
-        const handler = this._handlers.get(action);
-        if (typeof handler !== 'function') { return; }
+        const messageHandler = this._messageHandlers.get(action);
+        if (typeof messageHandler === 'undefined') { return; }
+
+        const {handler, async} = messageHandler;
 
         this._sendAck(port, id, senderId);
-        this._invokeHandler(handler, params, port, id, senderId);
+        if (async) {
+            this._invokeHandlerAsync(handler, params, port, id, senderId);
+        } else {
+            this._invokeHandler(handler, params, port, id, senderId);
+        }
     }
 
-    async _invokeHandler(handler, params, port, id, senderId) {
+    _invokeHandler(handler, params, port, id, senderId) {
+        try {
+            const result = handler(params);
+            this._sendResult(port, id, senderId, {result});
+        } catch (error) {
+            this._sendResult(port, id, senderId, {error: errorToJson(error)});
+        }
+    }
+
+    async _invokeHandlerAsync(handler, params, port, id, senderId) {
         try {
             const result = await handler(params);
             this._sendResult(port, id, senderId, {result});
diff --git a/ext/fg/js/popup-proxy-host.js b/ext/fg/js/popup-factory.js
similarity index 69%
rename from ext/fg/js/popup-proxy-host.js
rename to ext/fg/js/popup-factory.js
index 39150bc7..21e64dd0 100644
--- a/ext/fg/js/popup-proxy-host.js
+++ b/ext/fg/js/popup-factory.js
@@ -18,34 +18,29 @@
 /* global
  * FrontendApiReceiver
  * Popup
- * apiFrameInformationGet
  */
 
-class PopupProxyHost {
-    constructor() {
+class PopupFactory {
+    constructor(frameId) {
         this._popups = new Map();
-        this._frameId = null;
+        this._frameId = frameId;
     }
 
     // Public functions
 
     async prepare() {
-        const {frameId} = await apiFrameInformationGet();
-        if (typeof frameId !== 'number') { return; }
-        this._frameId = frameId;
-
-        const apiReceiver = new FrontendApiReceiver(`popup-proxy-host#${this._frameId}`, new Map([
-            ['getOrCreatePopup', this._onApiGetOrCreatePopup.bind(this)],
-            ['setOptionsContext', this._onApiSetOptionsContext.bind(this)],
-            ['hide', this._onApiHide.bind(this)],
-            ['isVisible', this._onApiIsVisibleAsync.bind(this)],
-            ['setVisibleOverride', this._onApiSetVisibleOverride.bind(this)],
-            ['containsPoint', this._onApiContainsPoint.bind(this)],
-            ['showContent', this._onApiShowContent.bind(this)],
-            ['setCustomCss', this._onApiSetCustomCss.bind(this)],
-            ['clearAutoPlayTimer', this._onApiClearAutoPlayTimer.bind(this)],
-            ['setContentScale', this._onApiSetContentScale.bind(this)],
-            ['getHostUrl', this._onApiGetHostUrl.bind(this)]
+        const apiReceiver = new FrontendApiReceiver(`popup-factory#${this._frameId}`, new Map([
+            ['getOrCreatePopup',   {async: false, handler: this._onApiGetOrCreatePopup.bind(this)}],
+            ['setOptionsContext',  {async: true,  handler: this._onApiSetOptionsContext.bind(this)}],
+            ['hide',               {async: false, handler: this._onApiHide.bind(this)}],
+            ['isVisible',          {async: true,  handler: this._onApiIsVisibleAsync.bind(this)}],
+            ['setVisibleOverride', {async: true,  handler: this._onApiSetVisibleOverride.bind(this)}],
+            ['containsPoint',      {async: true,  handler: this._onApiContainsPoint.bind(this)}],
+            ['showContent',        {async: true,  handler: this._onApiShowContent.bind(this)}],
+            ['setCustomCss',       {async: false, handler: this._onApiSetCustomCss.bind(this)}],
+            ['clearAutoPlayTimer', {async: false, handler: this._onApiClearAutoPlayTimer.bind(this)}],
+            ['setContentScale',    {async: false, handler: this._onApiSetContentScale.bind(this)}],
+            ['getUrl',             {async: false, handler: this._onApiGetUrl.bind(this)}]
         ]));
         apiReceiver.prepare();
     }
@@ -97,7 +92,7 @@ class PopupProxyHost {
 
     // API message handlers
 
-    async _onApiGetOrCreatePopup({id, parentId}) {
+    _onApiGetOrCreatePopup({id, parentId}) {
         const popup = this.getOrCreatePopup(id, parentId);
         return {
             id: popup.id
@@ -109,7 +104,7 @@ class PopupProxyHost {
         return await popup.setOptionsContext(optionsContext, source);
     }
 
-    async _onApiHide({id, changeFocus}) {
+    _onApiHide({id, changeFocus}) {
         const popup = this._getPopup(id);
         return popup.hide(changeFocus);
     }
@@ -126,33 +121,33 @@ class PopupProxyHost {
 
     async _onApiContainsPoint({id, x, y}) {
         const popup = this._getPopup(id);
-        [x, y] = PopupProxyHost._convertPopupPointToRootPagePoint(popup, x, y);
+        [x, y] = this._convertPopupPointToRootPagePoint(popup, x, y);
         return await popup.containsPoint(x, y);
     }
 
     async _onApiShowContent({id, elementRect, writingMode, type, details, context}) {
         const popup = this._getPopup(id);
-        elementRect = PopupProxyHost._convertJsonRectToDOMRect(popup, elementRect);
-        if (!PopupProxyHost._popupCanShow(popup)) { return; }
+        elementRect = this._convertJsonRectToDOMRect(popup, elementRect);
+        if (!this._popupCanShow(popup)) { return; }
         return await popup.showContent(elementRect, writingMode, type, details, context);
     }
 
-    async _onApiSetCustomCss({id, css}) {
+    _onApiSetCustomCss({id, css}) {
         const popup = this._getPopup(id);
         return popup.setCustomCss(css);
     }
 
-    async _onApiClearAutoPlayTimer({id}) {
+    _onApiClearAutoPlayTimer({id}) {
         const popup = this._getPopup(id);
         return popup.clearAutoPlayTimer();
     }
 
-    async _onApiSetContentScale({id, scale}) {
+    _onApiSetContentScale({id, scale}) {
         const popup = this._getPopup(id);
         return popup.setContentScale(scale);
     }
 
-    async _onApiGetHostUrl() {
+    _onApiGetUrl() {
         return window.location.href;
     }
 
@@ -166,12 +161,12 @@ class PopupProxyHost {
         return popup;
     }
 
-    static _convertJsonRectToDOMRect(popup, jsonRect) {
-        const [x, y] = PopupProxyHost._convertPopupPointToRootPagePoint(popup, jsonRect.x, jsonRect.y);
+    _convertJsonRectToDOMRect(popup, jsonRect) {
+        const [x, y] = this._convertPopupPointToRootPagePoint(popup, jsonRect.x, jsonRect.y);
         return new DOMRect(x, y, jsonRect.width, jsonRect.height);
     }
 
-    static _convertPopupPointToRootPagePoint(popup, x, y) {
+    _convertPopupPointToRootPagePoint(popup, x, y) {
         if (popup.parent !== null) {
             const popupRect = popup.parent.getContainerRect();
             x += popupRect.x;
@@ -180,7 +175,7 @@ class PopupProxyHost {
         return [x, y];
     }
 
-    static _popupCanShow(popup) {
+    _popupCanShow(popup) {
         return popup.parent === null || popup.parent.isVisibleSync();
     }
 }
diff --git a/ext/fg/js/popup-proxy.js b/ext/fg/js/popup-proxy.js
index 93418202..6a84e000 100644
--- a/ext/fg/js/popup-proxy.js
+++ b/ext/fg/js/popup-proxy.js
@@ -51,7 +51,7 @@ class PopupProxy {
     // Public functions
 
     async prepare() {
-        const {id} = await this._invokeHostApi('getOrCreatePopup', {id: this._id, parentId: this._parentId});
+        const {id} = await this._invoke('getOrCreatePopup', {id: this._id, parentId: this._parentId});
         this._id = id;
     }
 
@@ -60,19 +60,19 @@ class PopupProxy {
     }
 
     async setOptionsContext(optionsContext, source) {
-        return await this._invokeHostApi('setOptionsContext', {id: this._id, optionsContext, source});
+        return await this._invoke('setOptionsContext', {id: this._id, optionsContext, source});
     }
 
     hide(changeFocus) {
-        this._invokeHostApi('hide', {id: this._id, changeFocus});
+        this._invoke('hide', {id: this._id, changeFocus});
     }
 
     async isVisible() {
-        return await this._invokeHostApi('isVisible', {id: this._id});
+        return await this._invoke('isVisible', {id: this._id});
     }
 
     setVisibleOverride(visible) {
-        this._invokeHostApi('setVisibleOverride', {id: this._id, visible});
+        this._invoke('setVisibleOverride', {id: this._id, visible});
     }
 
     async containsPoint(x, y) {
@@ -80,7 +80,7 @@ class PopupProxy {
             await this._updateFrameOffset();
             [x, y] = this._applyFrameOffset(x, y);
         }
-        return await this._invokeHostApi('containsPoint', {id: this._id, x, y});
+        return await this._invoke('containsPoint', {id: this._id, x, y});
     }
 
     async showContent(elementRect, writingMode, type, details, context) {
@@ -90,32 +90,32 @@ class PopupProxy {
             [x, y] = this._applyFrameOffset(x, y);
         }
         elementRect = {x, y, width, height};
-        return await this._invokeHostApi('showContent', {id: this._id, elementRect, writingMode, type, details, context});
+        return await this._invoke('showContent', {id: this._id, elementRect, writingMode, type, details, context});
     }
 
-    async setCustomCss(css) {
-        return await this._invokeHostApi('setCustomCss', {id: this._id, css});
+    setCustomCss(css) {
+        this._invoke('setCustomCss', {id: this._id, css});
     }
 
     clearAutoPlayTimer() {
-        this._invokeHostApi('clearAutoPlayTimer', {id: this._id});
+        this._invoke('clearAutoPlayTimer', {id: this._id});
     }
 
-    async setContentScale(scale) {
-        this._invokeHostApi('setContentScale', {id: this._id, scale});
+    setContentScale(scale) {
+        this._invoke('setContentScale', {id: this._id, scale});
     }
 
-    async getHostUrl() {
-        return await this._invokeHostApi('getHostUrl', {});
+    async getUrl() {
+        return await this._invoke('getUrl', {});
     }
 
     // Private
 
-    _invokeHostApi(action, params={}) {
+    _invoke(action, params={}) {
         if (typeof this._parentFrameId !== 'number') {
             return Promise.reject(new Error('Invalid frame'));
         }
-        return this._apiSender.invoke(action, params, `popup-proxy-host#${this._parentFrameId}`);
+        return this._apiSender.invoke(action, params, `popup-factory#${this._parentFrameId}`);
     }
 
     async _updateFrameOffset() {
diff --git a/ext/fg/js/popup.js b/ext/fg/js/popup.js
index 7db53f0d..79b37251 100644
--- a/ext/fg/js/popup.js
+++ b/ext/fg/js/popup.js
@@ -139,7 +139,7 @@ class Popup {
         this._invokeApi('setContent', {type, details});
     }
 
-    async setCustomCss(css) {
+    setCustomCss(css) {
         this._invokeApi('setCustomCss', {css});
     }
 
diff --git a/ext/manifest.json b/ext/manifest.json
index 3cb634f0..80823fc4 100644
--- a/ext/manifest.json
+++ b/ext/manifest.json
@@ -44,9 +44,9 @@
             "fg/js/frontend-api-receiver.js",
             "fg/js/popup.js",
             "fg/js/source.js",
+            "fg/js/popup-factory.js",
             "fg/js/frame-offset-forwarder.js",
             "fg/js/popup-proxy.js",
-            "fg/js/popup-proxy-host.js",
             "fg/js/frontend.js",
             "fg/js/content-script-main.js"
         ],