これでOK

src/pages/achievements/[id]/index.tsx

@@ -1,6 +1,5 @@
 import { type ReactElement } from "react";
-import useSWR from "swr";
-// import useSWRImmutable from "swr/immutable";
+import useSWRImmutable from "swr/immutable";
 import { match } from "ts-pattern";
 import { useAchievements } from "@/hooks/db/achievements";
 import { useTeam } from "@/hooks/teams";
@@ -11,31 +10,36 @@ import { type Achievement } from "@/types/post-data/achievements";
 export default function Page(): ReactElement {
   const { id } = useParams("/achievements/:id");
   const { fetch } = useAchievements(useTeam);
-  const swrAchievement = useSWR("achievement", fetchAchievement);
+  const swrAchievement = useSWRImmutable("achievement", fetchAchievement);
 
-  async function fetchAchievement(): Promise<Achievement> {
+  async function fetchAchievement(): Promise<Achievement[]> {
     const achievements = await fetch();
 
     if (achievements == null) throw new Error("No unlockedAchievements found.");
 
-    const achievement = achievements.find((a) => a.id === Number(id));
-
-    if (achievement == null) throw new Error("No achievement found.");
-
-    return achievement;
+    return achievements;
   }
 
   return match(swrAchievement)
     .with(S.Loading, () => <p>Loading...</p>)
     .with(S.Success, ({ data }) => (
       <div>
-        <h1>name: {data.name}</h1>
-        <p>id: {data.id}</p>
-        <p>description: {data.description}</p>
-        <p>icon: {data.icon}</p>
-        <p>createdAt: {String(data.createdAt)}</p>
-        <p>updatedAt: {String(data.updatedAt)}</p>
-        <p>tags: {data.tags.map((tag) => tag.name).join(", ")}</p>
+        {data.map((d) => {
+          if (d.id === Number(id)) {
+            return (
+              <div key={d.id}>
+                <h1>name: {d.name}</h1>
+                <p>id: {d.id}</p>
+                <p>description: {d.description}</p>
+                <p>icon: {d.icon}</p>
+                <p>createdAt: {String(d.createdAt)}</p>
+                <p>updatedAt: {String(d.updatedAt)}</p>
+                <p>tags: {d.tags.map((tag) => tag.name).join(", ")}</p>
+              </div>
+            );
+          }
+          return null;
+        })}
       </div>
     ))
     .otherwise(({ error }) => {

src/pages/members/[id]/index.tsx

@@ -1,5 +1,4 @@
 import { type ReactElement } from "react";
-import useSWR from "swr";
 import useSWRImmutable from "swr/immutable";
 import { match } from "ts-pattern";
 import { useTeam } from "@/hooks/teams";