diff --git a/package-lock.json b/package-lock.json
index 43902175..4c6d6560 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -33,6 +33,9 @@
         "react-use": "^17.5.1",
         "web-vitals": "^2.1.4",
         "yaml": "^2.5.1"
+      },
+      "engines": {
+        "node": ">=22.0.0"
       }
     },
     "node_modules/@adobe/css-tools": {
diff --git a/src/components/Header.css b/src/components/Header.css
index a8375adf..386b275a 100644
--- a/src/components/Header.css
+++ b/src/components/Header.css
@@ -39,6 +39,20 @@
     margin-left: 0.5rem;
 }
 
+.header-language-toggle {
+    font-size: 14px;
+    padding: 0.4rem 0.6rem;
+    border: 1px solid var(--foreground2);
+    border-radius: 4px;
+    background-color: var(--background1);
+    transition: all 0.2s ease;
+}
+
+.header-language-toggle:hover {
+    background-color: var(--background2);
+    border-color: var(--foreground1);
+}
+
 @media (min-width: 768px) {
     .header {
         display: none;
diff --git a/src/components/Header.js b/src/components/Header.js
index fbffb503..95b7e519 100644
--- a/src/components/Header.js
+++ b/src/components/Header.js
@@ -1,9 +1,11 @@
 import { useContext, useState } from 'react';
 import SidebarContext from '../context/SidebarContext';
+import LanguageContext from '../context/LanguageContext';
 import './Header.css';
 
 export default function Header() {
   const { toggleSidebar } = useContext(SidebarContext);
+  const { language, toggleLanguage } = useContext(LanguageContext);
   const [isThree, setIsThree] = useState(true);
 
   const handlePlusClick = () => {
@@ -22,6 +24,13 @@ export default function Header() {
           <button onClick={handlePlusClick} className="header-button">
             ＋
           </button>
+          <button 
+            onClick={() => toggleLanguage(language === 'ja' ? 'en' : 'ja')} 
+            className="header-button header-language-toggle"
+            title={language === 'ja' ? 'Switch to English' : 'Switch to Japanese'}
+          >
+            {language === 'ja' ? 'EN' : 'JP'}
+          </button>
         </div>
       </div>
     </header>
diff --git a/src/components/SearchResult.js b/src/components/SearchResult.js
index 91a3ab8e..272dcd7d 100644
--- a/src/components/SearchResult.js
+++ b/src/components/SearchResult.js
@@ -97,19 +97,7 @@ function searchPostsByTags(posts, tags) {
     }, posts);
 }
 
-function findHighlightedText(content, query) {
-    const isMatch = content.toLowerCase().includes(query.toLowerCase());
 
-    const index = content.toLowerCase().indexOf(query.toLowerCase());
-    const start = Math.max(0, index - 10);
-    const end = Math.min(content.length, index + query.length + 100);
-    const before = content.slice(start, index);
-
-    const match = content.slice(index, index + query.length);
-    const after = content.slice(index + query.length, end);
-
-    return { isMatch, before, match, after };
-}
 
 // ドメイン名を抽出する関数
 function extractDomain(url) {