diff --git a/CHANGELOG.md b/CHANGELOG.md
index e8909c15da..36645aff74 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,7 +4,7 @@
 -
 
 ### Client
--
+- メールアドレス不要でCaptchaが有効な場合にアカウント登録完了後自動でのログインに失敗する問題を修正
 
 ### Server
 -
diff --git a/packages/frontend/src/account.ts b/packages/frontend/src/account.ts
index 84d89b1b3f..b91834b94f 100644
--- a/packages/frontend/src/account.ts
+++ b/packages/frontend/src/account.ts
@@ -226,7 +226,7 @@ export async function openAccountMenu(opts: {
 
 	function showSigninDialog() {
 		const { dispose } = popup(defineAsyncComponent(() => import('@/components/MkSigninDialog.vue')), {}, {
-			done: res => {
+			done: (res: Misskey.entities.SigninFlowResponse & { finished: true }) => {
 				addAccount(res.id, res.i);
 				success();
 			},
@@ -236,9 +236,9 @@ export async function openAccountMenu(opts: {
 
 	function createAccount() {
 		const { dispose } = popup(defineAsyncComponent(() => import('@/components/MkSignupDialog.vue')), {}, {
-			done: res => {
-				addAccount(res.id, res.i);
-				switchAccountWithToken(res.i);
+			done: (res: Misskey.entities.SignupResponse) => {
+				addAccount(res.id, res.token);
+				switchAccountWithToken(res.token);
 			},
 			closed: () => dispose(),
 		});
diff --git a/packages/frontend/src/components/MkSignin.vue b/packages/frontend/src/components/MkSignin.vue
index a79d7cf07a..a773cefdab 100644
--- a/packages/frontend/src/components/MkSignin.vue
+++ b/packages/frontend/src/components/MkSignin.vue
@@ -83,7 +83,7 @@ import type { AuthenticationPublicKeyCredential } from '@github/webauthn-json/br
 import type { OpenOnRemoteOptions } from '@/scripts/please-login.js';
 
 const emit = defineEmits<{
-	(ev: 'login', v: Misskey.entities.SigninFlowResponse): void;
+	(ev: 'login', v: Misskey.entities.SigninFlowResponse & { finished: true }): void;
 }>();
 
 const props = withDefaults(defineProps<{
@@ -276,7 +276,7 @@ async function tryLogin(req: Partial<Misskey.entities.SigninFlowRequest>): Promi
 	});
 }
 
-async function onLoginSucceeded(res: Misskey.entities.SigninFlowResponse & { finished: true; }) {
+async function onLoginSucceeded(res: Misskey.entities.SigninFlowResponse & { finished: true }) {
 	if (props.autoSet) {
 		await login(res.i);
 	}
diff --git a/packages/frontend/src/components/MkSigninDialog.vue b/packages/frontend/src/components/MkSigninDialog.vue
index 2aa11ac319..51dea960aa 100644
--- a/packages/frontend/src/components/MkSigninDialog.vue
+++ b/packages/frontend/src/components/MkSigninDialog.vue
@@ -23,6 +23,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 </template>
 
 <script lang="ts" setup>
+import * as Misskey from 'misskey-js';
 import { shallowRef } from 'vue';
 import type { OpenOnRemoteOptions } from '@/scripts/please-login.js';
 import MkSignin from '@/components/MkSignin.vue';
@@ -40,7 +41,7 @@ withDefaults(defineProps<{
 });
 
 const emit = defineEmits<{
-	(ev: 'done', v: any): void;
+	(ev: 'done', v: Misskey.entities.SigninFlowResponse & { finished: true }): void;
 	(ev: 'closed'): void;
 	(ev: 'cancelled'): void;
 }>();
@@ -52,7 +53,7 @@ function onClose() {
 	if (modal.value) modal.value.close();
 }
 
-function onLogin(res) {
+function onLogin(res: Misskey.entities.SigninFlowResponse & { finished: true }) {
 	emit('done', res);
 	if (modal.value) modal.value.close();
 }
diff --git a/packages/frontend/src/components/MkSignupDialog.form.vue b/packages/frontend/src/components/MkSignupDialog.form.vue
index a0c5488983..ffb5551ff3 100644
--- a/packages/frontend/src/components/MkSignupDialog.form.vue
+++ b/packages/frontend/src/components/MkSignupDialog.form.vue
@@ -98,7 +98,7 @@ const props = withDefaults(defineProps<{
 });
 
 const emit = defineEmits<{
-	(ev: 'signup', user: Misskey.entities.SigninFlowResponse): void;
+	(ev: 'signup', user: Misskey.entities.SignupResponse): void;
 	(ev: 'signupEmailPending'): void;
 }>();
 
@@ -250,18 +250,30 @@ async function onSubmit(): Promise<void> {
 	if (submitting.value) return;
 	submitting.value = true;
 
-	try {
-		await misskeyApi('signup', {
-			username: username.value,
-			password: password.value,
-			emailAddress: email.value,
-			invitationCode: invitationCode.value,
-			'hcaptcha-response': hCaptchaResponse.value,
-			'm-captcha-response': mCaptchaResponse.value,
-			'g-recaptcha-response': reCaptchaResponse.value,
-			'turnstile-response': turnstileResponse.value,
-		});
-		if (instance.emailRequiredForSignup) {
+	const signupPayload: Misskey.entities.SignupRequest = {
+		username: username.value,
+		password: password.value,
+		emailAddress: email.value,
+		invitationCode: invitationCode.value,
+		'hcaptcha-response': hCaptchaResponse.value,
+		'm-captcha-response': mCaptchaResponse.value,
+		'g-recaptcha-response': reCaptchaResponse.value,
+		'turnstile-response': turnstileResponse.value,
+	};
+
+	const res = await fetch(`${config.apiUrl}/signup`, {
+		method: 'POST',
+		headers: {
+			'Content-Type': 'application/json',
+		},
+		body: JSON.stringify(signupPayload),
+	}).catch(() => {
+		onSignupApiError();
+		return null;
+	});
+
+	if (res) {
+		if (res.status === 204 || instance.emailRequiredForSignup) {
 			os.alert({
 				type: 'success',
 				title: i18n.ts._signup.almostThere,
@@ -269,33 +281,31 @@ async function onSubmit(): Promise<void> {
 			});
 			emit('signupEmailPending');
 		} else {
-			const res = await misskeyApi('signin-flow', {
-				username: username.value,
-				password: password.value,
-			});
-			emit('signup', res);
+			const resJson = (await res.json()) as Misskey.entities.SignupResponse;
+			if (_DEV_) console.log(resJson);
 
-			if (props.autoSet && res.finished) {
-				return login(res.i);
-			} else {
-				os.alert({
-					type: 'error',
-					text: i18n.ts.somethingHappened,
-				});
+			emit('signup', resJson);
+
+			if (props.autoSet) {
+				await login(resJson.token);
 			}
 		}
-	} catch {
-		submitting.value = false;
-		hcaptcha.value?.reset?.();
-		mcaptcha.value?.reset?.();
-		recaptcha.value?.reset?.();
-		turnstile.value?.reset?.();
-
-		os.alert({
-			type: 'error',
-			text: i18n.ts.somethingHappened,
-		});
 	}
+
+	submitting.value = false;
+}
+
+function onSignupApiError() {
+	submitting.value = false;
+	hcaptcha.value?.reset?.();
+	mcaptcha.value?.reset?.();
+	recaptcha.value?.reset?.();
+	turnstile.value?.reset?.();
+
+	os.alert({
+		type: 'error',
+		text: i18n.ts.somethingHappened,
+	});
 }
 </script>
 
diff --git a/packages/frontend/src/components/MkSignupDialog.vue b/packages/frontend/src/components/MkSignupDialog.vue
index 4cccd99492..f240e6dc46 100644
--- a/packages/frontend/src/components/MkSignupDialog.vue
+++ b/packages/frontend/src/components/MkSignupDialog.vue
@@ -47,7 +47,7 @@ const props = withDefaults(defineProps<{
 });
 
 const emit = defineEmits<{
-	(ev: 'done', res: Misskey.entities.SigninFlowResponse): void;
+	(ev: 'done', res: Misskey.entities.SignupResponse): void;
 	(ev: 'closed'): void;
 }>();
 
@@ -55,7 +55,7 @@ const dialog = shallowRef<InstanceType<typeof MkModalWindow>>();
 
 const isAcceptedServerRule = ref(false);
 
-function onSignup(res: Misskey.entities.SigninFlowResponse) {
+function onSignup(res: Misskey.entities.SignupResponse) {
 	emit('done', res);
 	dialog.value?.close();
 }
diff --git a/packages/frontend/src/components/MkUserCardMini.vue b/packages/frontend/src/components/MkUserCardMini.vue
index b333722dc2..7a2e878931 100644
--- a/packages/frontend/src/components/MkUserCardMini.vue
+++ b/packages/frontend/src/components/MkUserCardMini.vue
@@ -23,7 +23,7 @@ import { acct } from '@/filters/user.js';
 
 const props = withDefaults(defineProps<{
 	user: Misskey.entities.User;
-	withChart: boolean;
+	withChart?: boolean;
 }>(), {
 	withChart: true,
 });
diff --git a/packages/frontend/src/pages/settings/accounts.vue b/packages/frontend/src/pages/settings/accounts.vue
index 08c9261dcf..1bbedb817e 100644
--- a/packages/frontend/src/pages/settings/accounts.vue
+++ b/packages/frontend/src/pages/settings/accounts.vue
@@ -45,7 +45,7 @@ const init = async () => {
 	});
 };
 
-function menu(account, ev) {
+function menu(account: Misskey.entities.UserDetailed, ev: MouseEvent) {
 	os.popupMenu([{
 		text: i18n.ts.switch,
 		icon: 'ti ti-switch-horizontal',
@@ -58,7 +58,7 @@ function menu(account, ev) {
 	}], ev.currentTarget ?? ev.target);
 }
 
-function addAccount(ev) {
+function addAccount(ev: MouseEvent) {
 	os.popupMenu([{
 		text: i18n.ts.existingAccount,
 		action: () => { addExistingAccount(); },
@@ -68,14 +68,14 @@ function addAccount(ev) {
 	}], ev.currentTarget ?? ev.target);
 }
 
-async function removeAccount(account) {
+async function removeAccount(account: Misskey.entities.UserDetailed) {
 	await _removeAccount(account.id);
 	accounts.value = accounts.value.filter(x => x.id !== account.id);
 }
 
 function addExistingAccount() {
 	const { dispose } = os.popup(defineAsyncComponent(() => import('@/components/MkSigninDialog.vue')), {}, {
-		done: async res => {
+		done: async (res: Misskey.entities.SigninFlowResponse & { finished: true }) => {
 			await addAccounts(res.id, res.i);
 			os.success();
 			init();
@@ -86,17 +86,17 @@ function addExistingAccount() {
 
 function createAccount() {
 	const { dispose } = os.popup(defineAsyncComponent(() => import('@/components/MkSignupDialog.vue')), {}, {
-		done: async res => {
-			await addAccounts(res.id, res.i);
-			switchAccountWithToken(res.i);
+		done: async (res: Misskey.entities.SignupResponse) => {
+			await addAccounts(res.id, res.token);
+			switchAccountWithToken(res.token);
 		},
 		closed: () => dispose(),
 	});
 }
 
 async function switchAccount(account: any) {
-	const fetchedAccounts: any[] = await getAccounts();
-	const token = fetchedAccounts.find(x => x.id === account.id).token;
+	const fetchedAccounts = await getAccounts();
+	const token = fetchedAccounts.find(x => x.id === account.id)!.token;
 	switchAccountWithToken(token);
 }
 
diff --git a/packages/misskey-js/etc/misskey-js.api.md b/packages/misskey-js/etc/misskey-js.api.md
index 1da8e4e613..72c236373d 100644
--- a/packages/misskey-js/etc/misskey-js.api.md
+++ b/packages/misskey-js/etc/misskey-js.api.md
@@ -3095,7 +3095,9 @@ type SigninWithPasskeyRequest = {
 
 // @public (undocumented)
 type SigninWithPasskeyResponse = {
-    signinResponse: SigninFlowResponse;
+    signinResponse: SigninFlowResponse & {
+        finished: true;
+    };
 };
 
 // @public (undocumented)
diff --git a/packages/misskey-js/src/entities.ts b/packages/misskey-js/src/entities.ts
index 2ffee40fba..dd88791ed0 100644
--- a/packages/misskey-js/src/entities.ts
+++ b/packages/misskey-js/src/entities.ts
@@ -308,7 +308,7 @@ export type SigninWithPasskeyInitResponse = {
 };
 
 export type SigninWithPasskeyResponse = {
-	signinResponse: SigninFlowResponse;
+	signinResponse: SigninFlowResponse & { finished: true };
 };
 
 type Values<T extends Record<PropertyKey, unknown>> = T[keyof T];