diff --git a/ext/bg/js/api.js b/ext/bg/js/api.js
index 4b2bacd7..b8ef4362 100644
--- a/ext/bg/js/api.js
+++ b/ext/bg/js/api.js
@@ -205,3 +205,8 @@ function apiForward(action, params, sender) {
         chrome.tabs.sendMessage(tabId, {action, params}, (response) => resolve(response));
     });
 }
+
+function apiFrameInformationGet(sender) {
+    const frameId = sender.frameId;
+    return Promise.resolve({frameId});
+}
diff --git a/ext/bg/js/backend.js b/ext/bg/js/backend.js
index 8f99c13a..39fd4288 100644
--- a/ext/bg/js/backend.js
+++ b/ext/bg/js/backend.js
@@ -127,6 +127,10 @@ class Backend {
 
             forward: ({action, params}) => {
                 forward(apiForward(action, params, sender), callback);
+            },
+
+            frameInformationGet: () => {
+                forward(apiFrameInformationGet(sender), callback);
             }
         };
 
diff --git a/ext/bg/js/search-frontend.js b/ext/bg/js/search-frontend.js
index 77aa4052..840a1ea8 100644
--- a/ext/bg/js/search-frontend.js
+++ b/ext/bg/js/search-frontend.js
@@ -25,8 +25,8 @@ async function searchFrontendSetup() {
         '/fg/js/api.js',
         '/fg/js/frontend-api-receiver.js',
         '/fg/js/popup.js',
-        '/fg/js/popup-proxy-host.js',
         '/fg/js/util.js',
+        '/fg/js/popup-proxy-host.js',
         '/fg/js/frontend.js'
     ];
     for (const src of scriptSrcs) {
diff --git a/ext/fg/js/api.js b/ext/fg/js/api.js
index 99ad307c..6bcb0dbb 100644
--- a/ext/fg/js/api.js
+++ b/ext/fg/js/api.js
@@ -64,3 +64,7 @@ function apiScreenshotGet(options) {
 function apiForward(action, params) {
     return utilInvoke('forward', {action, params});
 }
+
+function apiFrameInformationGet() {
+    return utilInvoke('frameInformationGet');
+}
diff --git a/ext/fg/js/frontend-api-receiver.js b/ext/fg/js/frontend-api-receiver.js
index f5d29f67..687e5c3c 100644
--- a/ext/fg/js/frontend-api-receiver.js
+++ b/ext/fg/js/frontend-api-receiver.js
@@ -31,7 +31,7 @@ class FrontendApiReceiver {
         port.onMessage.addListener(this.onMessage.bind(this, port));
     }
 
-    onMessage(port, {id, action, params, target}) {
+    onMessage(port, {id, action, params, target, senderId}) {
         if (
             target !== this.source ||
             !this.handlers.hasOwnProperty(action)
@@ -39,24 +39,24 @@ class FrontendApiReceiver {
             return;
         }
 
-        this.sendAck(port, id);
+        this.sendAck(port, id, senderId);
 
         const handler = this.handlers[action];
         handler(params).then(
             result => {
-                this.sendResult(port, id, {result});
+                this.sendResult(port, id, senderId, {result});
             },
             e => {
                 const error = typeof e.toString === 'function' ? e.toString() : e;
-                this.sendResult(port, id, {error});
+                this.sendResult(port, id, senderId, {error});
             });
     }
 
-    sendAck(port, id) {
-        port.postMessage({type: 'ack', id});
+    sendAck(port, id, senderId) {
+        port.postMessage({type: 'ack', id, senderId});
     }
 
-    sendResult(port, id, data) {
-        port.postMessage({type: 'result', id, data});
+    sendResult(port, id, senderId, data) {
+        port.postMessage({type: 'result', id, senderId, data});
     }
 }
diff --git a/ext/fg/js/frontend-api-sender.js b/ext/fg/js/frontend-api-sender.js
index e2becb90..a1cb02c4 100644
--- a/ext/fg/js/frontend-api-sender.js
+++ b/ext/fg/js/frontend-api-sender.js
@@ -19,6 +19,7 @@
 
 class FrontendApiSender {
     constructor() {
+        this.senderId = FrontendApiSender.generateId(16);
         this.ackTimeout = 3000; // 3 seconds
         this.responseTimeout = 10000; // 10 seconds
         this.callbacks = {};
@@ -43,11 +44,12 @@ class FrontendApiSender {
             this.callbacks[id] = info;
             info.timer = setTimeout(() => this.onError(id, 'Timeout (ack)'), this.ackTimeout);
 
-            this.port.postMessage({id, action, params, target});
+            this.port.postMessage({id, action, params, target, senderId: this.senderId});
         });
     }
 
-    onMessage({type, id, data}) {
+    onMessage({type, id, data, senderId}) {
+        if (senderId !== this.senderId) { return; }
         switch (type) {
             case 'ack':
                 this.onAck(id);
@@ -69,7 +71,7 @@ class FrontendApiSender {
 
     onAck(id) {
         if (!this.callbacks.hasOwnProperty(id)) {
-            console.warn(`ID ${id} not found`);
+            console.warn(`ID ${id} not found for ack`);
             return;
         }
 
diff --git a/ext/fg/js/frontend.js b/ext/fg/js/frontend.js
index d378dd61..9c511d8a 100644
--- a/ext/fg/js/frontend.js
+++ b/ext/fg/js/frontend.js
@@ -42,14 +42,20 @@ class Frontend {
         const isNested = (currentUrl === floatUrl);
 
         let id = null;
+        let parentFrameId = null;
         if (isNested) {
-            const match = /[&?]id=([^&]*?)(?:&|$)/.exec(location.href);
+            let match = /[&?]id=([^&]*?)(?:&|$)/.exec(location.href);
             if (match !== null) {
                 id = match[1];
             }
+
+            match = /[&?]parent=(\d+)(?:&|$)/.exec(location.href);
+            if (match !== null) {
+                parentFrameId = parseInt(match[1], 10);
+            }
         }
 
-        const popup = isNested ? new PopupProxy(id) : PopupProxyHost.instance.createPopup();
+        const popup = isNested ? new PopupProxy(id, parentFrameId) : PopupProxyHost.instance.createPopup(null);
         const frontend = new Frontend(popup);
         frontend.prepare();
         return frontend;
diff --git a/ext/fg/js/popup-proxy-host.js b/ext/fg/js/popup-proxy-host.js
index ba3db832..cdd1d02c 100644
--- a/ext/fg/js/popup-proxy-host.js
+++ b/ext/fg/js/popup-proxy-host.js
@@ -21,7 +21,22 @@ class PopupProxyHost {
     constructor() {
         this.popups = {};
         this.nextId = 0;
-        this.apiReceiver = new FrontendApiReceiver('popup-proxy-host', {
+        this.apiReceiver = null;
+        this.frameIdPromise = null;
+    }
+
+    static create() {
+        const popupProxyHost = new PopupProxyHost();
+        popupProxyHost.prepare();
+        return popupProxyHost;
+    }
+
+    async prepare() {
+        this.frameIdPromise = apiFrameInformationGet();
+        const {frameId} = await this.frameIdPromise;
+        if (typeof frameId !== 'number') { return; }
+
+        this.apiReceiver = new FrontendApiReceiver(`popup-proxy-host#${frameId}`, {
             createNestedPopup: ({parentId}) => this.createNestedPopup(parentId),
             show: ({id, elementRect, options}) => this.show(id, elementRect, options),
             showOrphaned: ({id, elementRect, options}) => this.show(id, elementRect, options),
@@ -39,7 +54,7 @@ class PopupProxyHost {
         const depth = (parent !== null ? parent.depth + 1 : 0);
         const id = `${this.nextId}`;
         ++this.nextId;
-        const popup = new Popup(id, depth);
+        const popup = new Popup(id, depth, this.frameIdPromise);
         if (parent !== null) {
             popup.parent = parent;
             parent.children.push(popup);
@@ -116,4 +131,4 @@ class PopupProxyHost {
     }
 }
 
-PopupProxyHost.instance = new PopupProxyHost();
+PopupProxyHost.instance = PopupProxyHost.create();
diff --git a/ext/fg/js/popup-proxy.js b/ext/fg/js/popup-proxy.js
index 3a15be7d..bbf6a2cf 100644
--- a/ext/fg/js/popup-proxy.js
+++ b/ext/fg/js/popup-proxy.js
@@ -18,12 +18,14 @@
 
 
 class PopupProxy {
-    constructor(parentId) {
+    constructor(parentId, parentFrameId) {
         this.parentId = parentId;
+        this.parentFrameId = parentFrameId;
         this.id = null;
         this.idPromise = null;
         this.parent = null;
         this.children = [];
+        this.depth = 0;
 
         this.container = null;
 
@@ -102,7 +104,10 @@ class PopupProxy {
     }
 
     invokeHostApi(action, params={}) {
-        return this.apiSender.invoke(action, params, 'popup-proxy-host');
+        if (typeof this.parentFrameId !== 'number') {
+            return Promise.reject('Invalid frame');
+        }
+        return this.apiSender.invoke(action, params, `popup-proxy-host#${this.parentFrameId}`);
     }
 
     static DOMRectToJson(domRect) {
diff --git a/ext/fg/js/popup.js b/ext/fg/js/popup.js
index 00dfeb89..24b5684d 100644
--- a/ext/fg/js/popup.js
+++ b/ext/fg/js/popup.js
@@ -18,38 +18,55 @@
 
 
 class Popup {
-    constructor(id, depth) {
+    constructor(id, depth, frameIdPromise) {
         this.id = id;
         this.depth = depth;
+        this.frameIdPromise = frameIdPromise;
+        this.frameId = null;
         this.parent = null;
         this.children = [];
         this.container = document.createElement('iframe');
         this.container.id = 'yomichan-float';
         this.container.addEventListener('mousedown', e => e.stopPropagation());
         this.container.addEventListener('scroll', e => e.stopPropagation());
-        this.container.setAttribute('src', chrome.extension.getURL(`/fg/float.html?id=${id}&depth=${depth}`));
         this.container.style.width = '0px';
         this.container.style.height = '0px';
-        this.injected = null;
+        this.injectPromise = null;
+        this.isInjected = false;
     }
 
     inject(options) {
-        if (!this.injected) {
-            this.injected = new Promise((resolve, reject) => {
-                this.container.addEventListener('load', () => {
-                    this.invokeApi('setOptions', {
-                        general: {
-                            customPopupCss: options.general.customPopupCss
-                        }
-                    });
-                    resolve();
-                });
-                this.observeFullscreen();
-                this.onFullscreenChanged();
-            });
+        if (this.injectPromise === null) {
+            this.injectPromise = this.createInjectPromise(options);
+        }
+        return this.injectPromise;
+    }
+
+    async createInjectPromise(options) {
+        try {
+            const {frameId} = await this.frameIdPromise;
+            if (typeof frameId === 'number') {
+                this.frameId = frameId;
+            }
+        } catch (e) {
+            // NOP
         }
 
-        return this.injected;
+        return new Promise((resolve) => {
+            const parent = (typeof this.frameId === 'number' ? this.frameId : '');
+            this.container.setAttribute('src', chrome.extension.getURL(`/fg/float.html?id=${this.id}&depth=${this.depth}&parent=${parent}`));
+            this.container.addEventListener('load', () => {
+                this.invokeApi('setOptions', {
+                    general: {
+                        customPopupCss: options.general.customPopupCss
+                    }
+                });
+                resolve();
+            });
+            this.observeFullscreen();
+            this.onFullscreenChanged();
+            this.isInjected = true;
+        });
     }
 
     async show(elementRect, writingMode, options) {
@@ -215,7 +232,7 @@ class Popup {
     }
 
     isVisible() {
-        return this.injected && this.container.style.visibility !== 'hidden';
+        return this.isInjected && this.container.style.visibility !== 'hidden';
     }
 
     setVisible(visible) {
@@ -260,7 +277,7 @@ class Popup {
     }
 
     clearAutoPlayTimer() {
-        if (this.injected) {
+        if (this.isInjected) {
             this.invokeApi('clearAutoPlayTimer');
         }
     }
diff --git a/ext/manifest.json b/ext/manifest.json
index eed6e40a..06d13dd1 100644
--- a/ext/manifest.json
+++ b/ext/manifest.json
@@ -23,9 +23,9 @@
             "fg/js/document.js",
             "fg/js/frontend-api-receiver.js",
             "fg/js/popup.js",
-            "fg/js/popup-proxy-host.js",
             "fg/js/source.js",
             "fg/js/util.js",
+            "fg/js/popup-proxy-host.js",
             "fg/js/frontend.js"
         ],
         "css": ["fg/css/client.css"],