diff --git a/.gitignore b/.gitignore
index 879cb66..bf77846 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 node_modules
 .direnv
+.wrangler
 CLAUDE.local.md
diff --git a/client/.env.preview b/client/.env.preview
index 831fe4f..3d69f54 100644
--- a/client/.env.preview
+++ b/client/.env.preview
@@ -1,2 +1,2 @@
-VITE_API_ENDPOINT=https://api.itsuhima-staging.utcode.net
+VITE_API_ENDPOINT=/api
 VITE_FRONTEND_ORIGIN=https://itsuhima-staging.utcode.net
diff --git a/client/.env.production b/client/.env.production
index 3fdbb58..ae35cf5 100644
--- a/client/.env.production
+++ b/client/.env.production
@@ -1,2 +1,2 @@
-VITE_API_ENDPOINT=https://api.itsuhima.utcode.net
+VITE_API_ENDPOINT=/api
 VITE_FRONTEND_ORIGIN=https://itsuhima.utcode.net
diff --git a/client/.gitignore b/client/.gitignore
index 438657a..fdc0972 100644
--- a/client/.gitignore
+++ b/client/.gitignore
@@ -13,6 +13,8 @@ dist-ssr
 *.local
 .env
 
+.wrangler
+
 # Editor directories and files
 .vscode/*
 !.vscode/extensions.json
diff --git a/client/functions/api/[[path]].ts b/client/functions/api/[[path]].ts
new file mode 100644
index 0000000..db356f3
--- /dev/null
+++ b/client/functions/api/[[path]].ts
@@ -0,0 +1,26 @@
+/// <reference types="@cloudflare/workers-types" />
+
+interface Env {
+  API_ENDPOINT: string;
+}
+
+// biome-ignore lint/suspicious/noExplicitAny: This is a Cloudflare Worker context
+export async function onRequest(context: EventContext<Env, any, any>): Promise<Response> {
+  const { request, env } = context;
+  const url = new URL(request.url);
+  const backendUrl = env.API_ENDPOINT + url.pathname.replace(/^\/api/, "") + url.search;
+
+  const proxied = new Request(backendUrl, {
+    method: request.method,
+    headers: request.headers,
+    body: request.method !== "GET" && request.method !== "HEAD" ? request.body : undefined,
+    redirect: "manual",
+  });
+
+  const response = await fetch(proxied);
+  return new Response(response.body, {
+    status: response.status,
+    statusText: response.statusText,
+    headers: response.headers,
+  });
+}
diff --git a/client/src/pages/eventId/Submission.tsx b/client/src/pages/eventId/Submission.tsx
index 51f8eb1..1ae3adb 100644
--- a/client/src/pages/eventId/Submission.tsx
+++ b/client/src/pages/eventId/Submission.tsx
@@ -135,7 +135,7 @@ export default function SubmissionPage() {
   const myGuestId = meAsGuest?.id;
   const isHost = project?.isHost;
 
-  const [mode, setMode] = useState<"view" | "edit" | "confirm">("edit");
+  const [mode, setMode] = useState<"view" | "edit" | "confirm">("view");
 
   const [guestName, setGuestName] = useState(meAsGuest?.name ?? "");
 
@@ -275,7 +275,7 @@ export default function SubmissionPage() {
 
   return (
     <>
-      <div className="flex h-[100dvh] flex-col bg-base-200">
+      <div className="flex h-dvh flex-col bg-base-200">
         <Header compact />
         {loading ? (
           <div className="flex w-full flex-1 items-center justify-center">
@@ -283,7 +283,7 @@ export default function SubmissionPage() {
           </div>
         ) : !project ? (
           <div className="mx-auto flex w-full max-w-7xl flex-col items-center justify-center gap-4 px-4 py-16 sm:px-6 lg:px-8">
-            <div className="flex min-h-[400px] w-full flex-col items-center justify-center gap-4 rounded-xl border border-base-300 bg-base-100 p-8 text-center shadow-sm">
+            <div className="flex min-h-100 w-full flex-col items-center justify-center gap-4 rounded-xl border border-base-300 bg-base-100 p-8 text-center shadow-sm">
               <p className="text-base-content/70 text-xl">イベントが見つかりませんでした。</p>
               <NavLink to="/" className="btn btn-primary">
                 ホームに戻る
@@ -414,7 +414,7 @@ export default function SubmissionPage() {
                               <p className="pt-1 font-medium text-base-content text-sm">{guest.name}</p>
                               {commentText && (
                                 <div className="mt-1.5 w-fit max-w-full rounded-2xl rounded-tl-none bg-base-300 px-3 py-2 text-base-content text-sm">
-                                  <span className="whitespace-pre-wrap break-words">{commentText}</span>
+                                  <span className="wrap-break-word whitespace-pre-wrap">{commentText}</span>
                                 </div>
                               )}
                             </div>
@@ -449,27 +449,31 @@ export default function SubmissionPage() {
                         }}
                       >
                         <LuPencil className="h-4 w-4" />
-                        <span className="hidden sm:inline">日程を変更する</span>
-                        <span className="sm:hidden">日程変更</span>
+                        {meAsGuest ? (
+                          <>
+                            <span className="hidden sm:inline">日程を変更する</span>
+                            <span className="sm:hidden">日程変更</span>
+                          </>
+                        ) : (
+                          <span>提出する</span>
+                        )}
                       </button>
                     </div>
                   ) : (
                     <div className="flex items-center justify-between gap-2">
-                      {!!myGuestId && (
-                        <button
-                          type="button"
-                          className="btn btn-sm btn-outline shrink-0"
-                          disabled={loading}
-                          onClick={() => {
-                            setEditingSlots([]);
-                            setGuestName(meAsGuest?.name ?? "");
-                            setComment(meAsGuest?.comment ?? "");
-                            setMode("view");
-                          }}
-                        >
-                          <span>キャンセル</span>
-                        </button>
-                      )}
+                      <button
+                        type="button"
+                        className="btn btn-sm btn-outline shrink-0"
+                        disabled={loading}
+                        onClick={() => {
+                          setEditingSlots(meAsGuest?.slots ?? []);
+                          setGuestName(meAsGuest?.name ?? "");
+                          setComment(meAsGuest?.comment ?? "");
+                          setMode("view");
+                        }}
+                      >
+                        <span>キャンセル</span>
+                      </button>
                       <button
                         type="button"
                         className="btn btn-sm btn-primary ml-auto inline-flex shrink-0 gap-1.5"