diff --git a/ext/api.js b/ext/api.js
index 6e9d6f4f..496f8be3 100644
--- a/ext/api.js
+++ b/ext/api.js
@@ -18,7 +18,7 @@
 
 
 function sendMessage(action, data, callback) {
-    window.chrome.runtime.sendMessage({action: action, data: data}, callback);
+    chrome.runtime.sendMessage({action: action, data: data}, callback);
 }
 
 function findTerm(text, callback) {
diff --git a/ext/background.html b/ext/background.html
index 09a21779..665bc968 100644
--- a/ext/background.html
+++ b/ext/background.html
@@ -5,6 +5,6 @@
     <script src="jp/dictionary.js"></script>
     <script src="jp/deinflector.js"></script>
     <script src="jp/translator.js"></script>
-    <script src="jp/api.js"></script>
+    <script src="jp/yomichan.js"></script>
 </body>
 </html>
diff --git a/ext/jp/api.js b/ext/jp/api.js
deleted file mode 100644
index 216b961f..00000000
--- a/ext/jp/api.js
+++ /dev/null
@@ -1,55 +0,0 @@
-/*
- * Copyright (C) 2016  Alex Yatskov <alex@foosoft.net>
- * Author: Alex Yatskov <alex@foosoft.net>
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-
-
-function onFindTerm({term}) {
-    return window.trans.findTerm(term);
-}
-
-function onMessage(request, sender, callback) {
-    const {action, data} = request;
-
-    const handler = {
-        findTerm: onFindTerm
-    }[action];
-
-    if (handler !== null) {
-        const result = handler(data);
-        if (callback !== null) {
-            callback(result);
-        }
-    }
-}
-
-function onInit() {
-    chrome.runtime.onMessage.addListener(onMessage);
-
-    const res1 = window.trans.findTerm('食べられない');
-    const res2 = window.trans.findTerm('作られている');
-}
-
-(() => {
-    const res =  {
-        rules:    'jp/data/rules.json',
-        edict:    'jp/data/edict.json',
-        enamdict: 'jp/data/enamdict.json',
-        kanjidic: 'jp/data/kanjidic.json'
-    };
-
-    window.trans = new Translator(res, onInit);
-})();
diff --git a/ext/jp/translator.js b/ext/jp/translator.js
index aef20f19..7a610377 100644
--- a/ext/jp/translator.js
+++ b/ext/jp/translator.js
@@ -18,9 +18,17 @@
 
 
 class Translator {
-    constructor(paths, callback) {
+    constructor() {
         this.dictionary  = new Dictionary();
         this.deinflector = new Deinflector();
+        this.initialized = false;
+    }
+
+    loadData(paths, callback) {
+        if (this.initialized) {
+            callback();
+            return;
+        }
 
         const loaders = [];
         for (const key of ['rules', 'edict', 'enamdict', 'kanjidic']) {
diff --git a/ext/jp/yomichan.js b/ext/jp/yomichan.js
new file mode 100644
index 00000000..5c2b579f
--- /dev/null
+++ b/ext/jp/yomichan.js
@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2016  Alex Yatskov <alex@foosoft.net>
+ * Author: Alex Yatskov <alex@foosoft.net>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+class Yomichan {
+    constructor() {
+        this.translator = new Translator();
+        this.res = {
+            rules:    'jp/data/rules.json',
+            edict:    'jp/data/edict.json',
+            enamdict: 'jp/data/enamdict.json',
+            kanjidic: 'jp/data/kanjidic.json'
+        };
+
+        this.updateState('disabled');
+
+        chrome.runtime.onMessage.addListener(this.onMessage.bind(this));
+        chrome.browserAction.onClicked.addListener(this.onBrowserAction.bind(this));
+    }
+
+    onFindTerm({term}) {
+        return this.translator.findTerm(term);
+    }
+
+    onMessage(request, sender, callback) {
+        const {action, data} = request;
+        const handler = {
+            findTerm: this.onFindTerm
+        }[action];
+
+        if (handler !== null) {
+            const result = handler.call(this, data);
+            if (callback !== null) {
+                callback(result);
+            }
+        }
+    }
+
+    onBrowserAction(tab) {
+        switch (this.state) {
+            case 'disabled':
+                this.updateState('loading');
+                this.translator.loadData(this.res, () => this.updateState('enabled'));
+                break;
+            case 'enabled':
+                this.updateState('disabled');
+                break;
+        }
+    }
+
+    updateState(state) {
+        const text = {'disabled': '', 'enabled': 'on', 'loading': '...'}[state];
+        chrome.browserAction.setBadgeText({text: text});
+        this.state = state;
+    }
+}
+
+window.yomichan = new Yomichan();