diff --git a/.envrc b/.envrc
new file mode 100644
index 00000000..1d953f4b
--- /dev/null
+++ b/.envrc
@@ -0,0 +1 @@
+use nix
diff --git a/src/components/GlobalFooter.tsx b/src/components/GlobalFooter.tsx
index a98b87ba..de7d7d57 100644
--- a/src/components/GlobalFooter.tsx
+++ b/src/components/GlobalFooter.tsx
@@ -74,7 +74,7 @@ export default function GlobalFooter({ className }: { className?: string }) {
                 to: "https://first-programming.utcode.net/",
               },
               { title: "GitHub", to: "https://github.com/ut-code" },
-              { title: "𝕏", to: "https://twitter.com/utokyo_code" },
+              { title: "X", to: "https://twitter.com/utokyo_code" },
             ]}
           />
         </div>
diff --git a/src/pages/contact.tsx b/src/pages/contact.tsx
index 3743e454..91b28742 100644
--- a/src/pages/contact.tsx
+++ b/src/pages/contact.tsx
@@ -34,7 +34,7 @@ export default function ContactPage() {
           <p>ut.code(); へのお問い合わせは、各種 SNS をご利用ください。</p>
           <p className="not-prose flex gap-4">
             <ActionButton to="https://twitter.com/utokyo_code">
-              𝕏 (旧 Twitter)
+              X (旧 Twitter)
             </ActionButton>
             <ActionButton to="https://line.me/ti/p/%40nlr3843e">
               LINE
diff --git a/src/pages/index.tsx b/src/pages/index.tsx
index 17744a14..7e75a99b 100644
--- a/src/pages/index.tsx
+++ b/src/pages/index.tsx
@@ -188,7 +188,7 @@ export default function IndexPage({ data }: PageProps<Queries.IndexPageQuery>) {
               { title: "構成人数", content: "20 名程度 (アクティブ)" },
               { title: "部室", content: "駒場キャンパス学生会館 313B 教室" },
               {
-                title: "𝕏",
+                title: "X",
                 content: "@utokyo_code",
                 link: "https://x.com/utokyo_code",
               },
diff --git a/src/templates/member.tsx b/src/templates/member.tsx
index 0799b5ec..01aab87a 100644
--- a/src/templates/member.tsx
+++ b/src/templates/member.tsx
@@ -5,6 +5,7 @@ import nullthrows from "nullthrows";
 import Color from "color";
 import clsx from "clsx";
 import { FiGithub, FiGlobe } from "react-icons/fi";
+import { FaXTwitter } from "react-icons/fa6";
 import GlobalHeader from "../components/GlobalHeader";
 import GlobalFooter from "../components/GlobalFooter";
 import CommonHead from "../components/CommonHead";
@@ -66,9 +67,9 @@ export default function MemberPage({
                     target="_blank"
                     className={socialButtonClassName}
                     rel="noreferrer"
-                    aria-label="𝕏 (旧 Twitter) を見る"
+                    aria-label="X (旧 Twitter) を見る"
                   >
-                    𝕏
+                    <FaXTwitter />
                   </a>
                 )}
                 {data.mdx?.frontmatter?.website && (