diff --git a/src/components/app-shell.tsx b/src/components/app-shell.tsx
new file mode 100644
index 0000000..8cffced
--- /dev/null
+++ b/src/components/app-shell.tsx
@@ -0,0 +1,34 @@
+import { Link } from '@tanstack/react-router'
+
+export function AppShell({
+  active,
+  children,
+}: {
+  active: 'user' | 'search'
+  children: React.ReactNode
+}) {
+  return (
+    <main className="app">
+      <header className="app-header">
+        <p className="brand">TWITTER LITE</p>
+        <nav aria-label="閲覧方法" className="tabs">
+          <Link
+            aria-current={active === 'user' ? 'page' : undefined}
+            search={{ target: '' }}
+            to="/user"
+          >
+            ユーザー
+          </Link>
+          <Link
+            aria-current={active === 'search' ? 'page' : undefined}
+            search={{ q: '', product: 'Latest', following: false }}
+            to="/search"
+          >
+            検索
+          </Link>
+        </nav>
+      </header>
+      <section className="reader">{children}</section>
+    </main>
+  )
+}
diff --git a/src/features/posts/components/forms.test.tsx b/src/features/posts/components/forms.test.tsx
new file mode 100644
index 0000000..0c68e0a
--- /dev/null
+++ b/src/features/posts/components/forms.test.tsx
@@ -0,0 +1,57 @@
+import { fireEvent, render, screen } from '@testing-library/react'
+import { describe, expect, it, vi } from 'vitest'
+import { SearchForm } from './search-form'
+import { UserForm } from './user-form'
+
+describe('UserForm', () => {
+  it('submits only after the user enters a target', () => {
+    const onSubmit = vi.fn()
+    render(<UserForm initialTarget="" onSubmit={onSubmit} />)
+
+    fireEvent.change(screen.getByLabelText('ハンドルまたはプロフィール URL'), {
+      target: { value: '@yuta' },
+    })
+    fireEvent.click(screen.getByRole('button', { name: '表示' }))
+
+    expect(onSubmit).toHaveBeenCalledWith('yuta')
+  })
+
+  it('explains invalid input beside the field', () => {
+    const onSubmit = vi.fn()
+    render(<UserForm initialTarget="" onSubmit={onSubmit} />)
+
+    fireEvent.click(screen.getByRole('button', { name: '表示' }))
+
+    expect(screen.getByRole('alert')).toHaveTextContent(
+      'ハンドルまたはプロフィール URL を入力してください。',
+    )
+    expect(onSubmit).not.toHaveBeenCalled()
+  })
+})
+
+describe('SearchForm', () => {
+  it('submits the selected ranking and follows filter', () => {
+    const onSubmit = vi.fn()
+    render(
+      <SearchForm
+        initialQuery=""
+        initialProduct="Latest"
+        initialFollowing={false}
+        onSubmit={onSubmit}
+      />,
+    )
+
+    fireEvent.change(screen.getByLabelText('検索語'), {
+      target: { value: 'AI lang:ja' },
+    })
+    fireEvent.click(screen.getByLabelText('人気順'))
+    fireEvent.click(screen.getByLabelText('フォロー中のみ'))
+    fireEvent.click(screen.getByRole('button', { name: '検索' }))
+
+    expect(onSubmit).toHaveBeenCalledWith({
+      q: 'AI lang:ja',
+      product: 'Top',
+      following: true,
+    })
+  })
+})
diff --git a/src/features/posts/components/search-form.tsx b/src/features/posts/components/search-form.tsx
new file mode 100644
index 0000000..0a58a50
--- /dev/null
+++ b/src/features/posts/components/search-form.tsx
@@ -0,0 +1,87 @@
+import type { SearchProduct } from '@yuta/bird'
+import { type FormEvent, useState } from 'react'
+import { buildSearchQuery } from '../inputs'
+
+type SearchValues = {
+  q: string
+  product: SearchProduct
+  following: boolean
+}
+
+type Props = {
+  initialQuery: string
+  initialProduct: SearchProduct
+  initialFollowing: boolean
+  onSubmit: (values: SearchValues) => void
+}
+
+export function SearchForm({
+  initialQuery,
+  initialProduct,
+  initialFollowing,
+  onSubmit,
+}: Props) {
+  const [q, setQuery] = useState(initialQuery)
+  const [product, setProduct] = useState(initialProduct)
+  const [following, setFollowing] = useState(initialFollowing)
+  const [error, setError] = useState('')
+
+  const submit = (event: FormEvent) => {
+    event.preventDefault()
+    try {
+      const query = buildSearchQuery(q, false)
+      setError('')
+      onSubmit({ q: query, product, following })
+    } catch (cause) {
+      setError(
+        cause instanceof Error ? cause.message : '入力内容を確認してください。',
+      )
+    }
+  }
+
+  return (
+    <form className="intent-form" onSubmit={submit}>
+      <label className="field">
+        <span>検索語</span>
+        <input
+          autoComplete="off"
+          aria-describedby={error ? 'query-error' : undefined}
+          aria-invalid={Boolean(error)}
+          name="q"
+          value={q}
+          onChange={(event) => setQuery(event.currentTarget.value)}
+          placeholder="検索語や高度な検索演算子"
+        />
+        {error ? (
+          <span className="field-error" id="query-error" role="alert">
+            {error}
+          </span>
+        ) : null}
+      </label>
+      <fieldset className="segmented">
+        <legend>並び順</legend>
+        {(['Top', 'Latest'] as const).map((value) => (
+          <label key={value}>
+            <input
+              checked={product === value}
+              name="product"
+              onChange={() => setProduct(value)}
+              type="radio"
+              value={value}
+            />
+            {value === 'Top' ? '人気順' : '最新順'}
+          </label>
+        ))}
+      </fieldset>
+      <label className="check">
+        <input
+          checked={following}
+          onChange={(event) => setFollowing(event.currentTarget.checked)}
+          type="checkbox"
+        />
+        フォロー中のみ
+      </label>
+      <button type="submit">検索</button>
+    </form>
+  )
+}
diff --git a/src/features/posts/components/user-form.tsx b/src/features/posts/components/user-form.tsx
new file mode 100644
index 0000000..e5c8608
--- /dev/null
+++ b/src/features/posts/components/user-form.tsx
@@ -0,0 +1,47 @@
+import { type FormEvent, useState } from 'react'
+import { normalizeUserTarget } from '../inputs'
+
+type Props = {
+  initialTarget: string
+  onSubmit: (target: string) => void
+}
+
+export function UserForm({ initialTarget, onSubmit }: Props) {
+  const [target, setTarget] = useState(initialTarget)
+  const [error, setError] = useState('')
+  const submit = (event: FormEvent) => {
+    event.preventDefault()
+    try {
+      const handle = normalizeUserTarget(target)
+      setError('')
+      onSubmit(handle)
+    } catch (cause) {
+      setError(
+        cause instanceof Error ? cause.message : '入力内容を確認してください。',
+      )
+    }
+  }
+
+  return (
+    <form className="intent-form" onSubmit={submit}>
+      <label className="field">
+        <span>ハンドルまたはプロフィール URL</span>
+        <input
+          autoComplete="off"
+          aria-describedby={error ? 'target-error' : undefined}
+          aria-invalid={Boolean(error)}
+          name="target"
+          value={target}
+          onChange={(event) => setTarget(event.currentTarget.value)}
+          placeholder="@handle または https://x.com/handle"
+        />
+        {error ? (
+          <span className="field-error" id="target-error" role="alert">
+            {error}
+          </span>
+        ) : null}
+      </label>
+      <button type="submit">表示</button>
+    </form>
+  )
+}
diff --git a/src/routeTree.gen.ts b/src/routeTree.gen.ts
index dceedff..f0c1d42 100644
--- a/src/routeTree.gen.ts
+++ b/src/routeTree.gen.ts
@@ -9,8 +9,20 @@
 // Additionally, you should also exclude this file from your linter and/or formatter to prevent it from being checked or modified.
 
 import { Route as rootRouteImport } from './routes/__root'
+import { Route as UserRouteImport } from './routes/user'
+import { Route as SearchRouteImport } from './routes/search'
 import { Route as IndexRouteImport } from './routes/index'
 
+const UserRoute = UserRouteImport.update({
+  id: '/user',
+  path: '/user',
+  getParentRoute: () => rootRouteImport,
+} as any)
+const SearchRoute = SearchRouteImport.update({
+  id: '/search',
+  path: '/search',
+  getParentRoute: () => rootRouteImport,
+} as any)
 const IndexRoute = IndexRouteImport.update({
   id: '/',
   path: '/',
@@ -19,28 +31,50 @@ const IndexRoute = IndexRouteImport.update({
 
 export interface FileRoutesByFullPath {
   '/': typeof IndexRoute
+  '/search': typeof SearchRoute
+  '/user': typeof UserRoute
 }
 export interface FileRoutesByTo {
   '/': typeof IndexRoute
+  '/search': typeof SearchRoute
+  '/user': typeof UserRoute
 }
 export interface FileRoutesById {
   __root__: typeof rootRouteImport
   '/': typeof IndexRoute
+  '/search': typeof SearchRoute
+  '/user': typeof UserRoute
 }
 export interface FileRouteTypes {
   fileRoutesByFullPath: FileRoutesByFullPath
-  fullPaths: '/'
+  fullPaths: '/' | '/search' | '/user'
   fileRoutesByTo: FileRoutesByTo
-  to: '/'
-  id: '__root__' | '/'
+  to: '/' | '/search' | '/user'
+  id: '__root__' | '/' | '/search' | '/user'
   fileRoutesById: FileRoutesById
 }
 export interface RootRouteChildren {
   IndexRoute: typeof IndexRoute
+  SearchRoute: typeof SearchRoute
+  UserRoute: typeof UserRoute
 }
 
 declare module '@tanstack/react-router' {
   interface FileRoutesByPath {
+    '/user': {
+      id: '/user'
+      path: '/user'
+      fullPath: '/user'
+      preLoaderRoute: typeof UserRouteImport
+      parentRoute: typeof rootRouteImport
+    }
+    '/search': {
+      id: '/search'
+      path: '/search'
+      fullPath: '/search'
+      preLoaderRoute: typeof SearchRouteImport
+      parentRoute: typeof rootRouteImport
+    }
     '/': {
       id: '/'
       path: '/'
@@ -53,6 +87,8 @@ declare module '@tanstack/react-router' {
 
 const rootRouteChildren: RootRouteChildren = {
   IndexRoute: IndexRoute,
+  SearchRoute: SearchRoute,
+  UserRoute: UserRoute,
 }
 export const routeTree = rootRouteImport
   ._addFileChildren(rootRouteChildren)
diff --git a/src/routes/index.test.tsx b/src/routes/index.test.tsx
deleted file mode 100644
index 0ab01cb..0000000
--- a/src/routes/index.test.tsx
+++ /dev/null
@@ -1,12 +0,0 @@
-import { render, screen } from '@testing-library/react'
-import { describe, expect, it } from 'vitest'
-import { Home } from './index'
-
-describe('Home', () => {
-  it('starts without ambient post content', () => {
-    render(<Home />)
-
-    expect(screen.getByText('目的を決めてから開く')).toBeInTheDocument()
-    expect(screen.queryByRole('article')).not.toBeInTheDocument()
-  })
-})
diff --git a/src/routes/index.tsx b/src/routes/index.tsx
index 8cde3a5..ca7971e 100644
--- a/src/routes/index.tsx
+++ b/src/routes/index.tsx
@@ -1,13 +1,7 @@
-import { createFileRoute } from '@tanstack/react-router'
+import { createFileRoute, redirect } from '@tanstack/react-router'
 
-export const Route = createFileRoute('/')({ component: Home })
-
-export function Home() {
-  return (
-    <main className="landing">
-      <p className="brand">TWITTER LITE</p>
-      <h1>目的を決めてから開く</h1>
-      <p>ユーザー名か検索語を入力するまで、投稿は表示しません。</p>
-    </main>
-  )
-}
+export const Route = createFileRoute('/')({
+  beforeLoad: () => {
+    throw redirect({ to: '/user', search: { target: '' } })
+  },
+})
diff --git a/src/routes/search.tsx b/src/routes/search.tsx
new file mode 100644
index 0000000..861f363
--- /dev/null
+++ b/src/routes/search.tsx
@@ -0,0 +1,27 @@
+import { createFileRoute } from '@tanstack/react-router'
+import { AppShell } from '#/components/app-shell'
+import { SearchForm } from '#/features/posts/components/search-form'
+import { postSearchRouteSchema } from '#/features/posts/inputs'
+
+export const Route = createFileRoute('/search')({
+  validateSearch: (search) => postSearchRouteSchema.parse(search),
+  component: SearchRoute,
+})
+
+function SearchRoute() {
+  const values = Route.useSearch()
+  const navigate = Route.useNavigate()
+  return (
+    <AppShell active="search">
+      <h1>何を確認しますか？</h1>
+      <p className="intro">入力した条件だけを検索します。</p>
+      <SearchForm
+        initialFollowing={values.following}
+        initialProduct={values.product}
+        initialQuery={values.q}
+        key={`${values.q}:${values.product}:${values.following}`}
+        onSubmit={(search) => navigate({ search })}
+      />
+    </AppShell>
+  )
+}
diff --git a/src/routes/user.tsx b/src/routes/user.tsx
new file mode 100644
index 0000000..3cf08f9
--- /dev/null
+++ b/src/routes/user.tsx
@@ -0,0 +1,25 @@
+import { createFileRoute } from '@tanstack/react-router'
+import { AppShell } from '#/components/app-shell'
+import { UserForm } from '#/features/posts/components/user-form'
+import { userRouteSearchSchema } from '#/features/posts/inputs'
+
+export const Route = createFileRoute('/user')({
+  validateSearch: (search) => userRouteSearchSchema.parse(search),
+  component: UserRoute,
+})
+
+function UserRoute() {
+  const { target } = Route.useSearch()
+  const navigate = Route.useNavigate()
+  return (
+    <AppShell active="user">
+      <h1>誰の投稿を見ますか？</h1>
+      <p className="intro">履歴やおすすめは表示しません。</p>
+      <UserForm
+        initialTarget={target}
+        key={target}
+        onSubmit={(nextTarget) => navigate({ search: { target: nextTarget } })}
+      />
+    </AppShell>
+  )
+}
diff --git a/src/styles.css b/src/styles.css
index 3bf67db..c5aa430 100644
--- a/src/styles.css
+++ b/src/styles.css
@@ -2,6 +2,7 @@
   color: #1e3238;
   background: #dfe7e9;
   font-family: Inter, "Noto Sans JP", ui-sans-serif, system-ui, sans-serif;
+  color-scheme: light;
 }
 
 * {
@@ -12,6 +13,7 @@ body {
   min-width: 320px;
   min-height: 100vh;
   margin: 0;
+  background: #dfe7e9;
 }
 
 button,
@@ -19,17 +21,193 @@ input {
   font: inherit;
 }
 
-.landing {
-  width: min(42rem, calc(100% - 2rem));
-  margin: 15vh auto;
-  padding: 2rem;
+.app {
+  width: min(52rem, calc(100% - 2rem));
+  margin: clamp(2rem, 10vh, 6rem) auto;
+}
+
+.app-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 1rem;
+  padding: 0 0.25rem 0.75rem;
+}
+
+.brand {
+  margin: 0;
+  color: #70858a;
+  font-size: 0.7rem;
+  font-weight: 700;
+  letter-spacing: 0.2em;
+}
+
+.tabs {
+  display: grid;
+  grid-template-columns: repeat(2, minmax(5.5rem, 1fr));
+  gap: 0.2rem;
+  padding: 0.2rem;
+  border: 1px solid #c1cfd2;
+  border-radius: 0.6rem;
+  background: #f8faf9;
+}
+
+.tabs a {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 0.45rem;
+  padding: 0.45rem 0.75rem;
+  border-radius: 0.4rem;
+  color: #70858a;
+  font-size: 0.82rem;
+  font-weight: 700;
+  text-decoration: none;
+}
+
+.tabs a[aria-current="page"] {
+  color: #f8faf9;
+  background: #1e3238;
+}
+
+.tabs a[aria-current="page"]::before {
+  width: 0.35rem;
+  height: 0.35rem;
+  border-radius: 50%;
+  background: currentColor;
+  content: "";
+}
+
+.tabs a:focus-visible,
+button:focus-visible,
+input:focus-visible {
+  outline: 3px solid #70858a;
+  outline-offset: 2px;
+}
+
+.reader {
+  padding: clamp(1.5rem, 5vw, 3rem);
   border: 1px solid #c1cfd2;
   border-radius: 1rem;
   background: #f8faf9;
 }
 
-.brand {
+.reader h1 {
+  max-width: 18ch;
+  margin: 0;
+  font-size: clamp(1.65rem, 5vw, 2.35rem);
+  font-weight: 650;
+  letter-spacing: -0.04em;
+  line-height: 1.2;
+}
+
+.intro {
+  margin: 0.75rem 0 2rem;
   color: #70858a;
-  font-size: 0.7rem;
-  letter-spacing: 0.2em;
+  line-height: 1.7;
+}
+
+.intent-form {
+  display: grid;
+  gap: 1.25rem;
+  max-width: 36rem;
+}
+
+.field {
+  display: grid;
+  gap: 0.5rem;
+  color: #1e3238;
+  font-size: 0.84rem;
+  font-weight: 700;
+}
+
+.field input {
+  width: 100%;
+  min-height: 2.8rem;
+  padding: 0.65rem 0.8rem;
+  border: 1px solid #c1cfd2;
+  border-radius: 0.5rem;
+  color: #1e3238;
+  background: #f8faf9;
+}
+
+.field input::placeholder {
+  color: #70858a;
+  font-weight: 400;
+}
+
+.field input[aria-invalid="true"] {
+  border-color: #70858a;
+}
+
+.field-error {
+  color: #1e3238;
+  font-size: 0.78rem;
+  font-weight: 600;
+}
+
+.segmented {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0.75rem 1rem;
+  margin: 0;
+  padding: 0;
+  border: 0;
+}
+
+.segmented legend {
+  width: 100%;
+  margin-bottom: 0.1rem;
+  font-size: 0.84rem;
+  font-weight: 700;
+}
+
+.segmented label,
+.check {
+  display: inline-flex;
+  align-items: center;
+  gap: 0.45rem;
+  font-size: 0.86rem;
+}
+
+.segmented input,
+.check input {
+  accent-color: #1e3238;
+}
+
+.intent-form button {
+  justify-self: start;
+  min-width: 7rem;
+  min-height: 2.7rem;
+  padding: 0.55rem 1rem;
+  border: 1px solid #1e3238;
+  border-radius: 0.5rem;
+  color: #f8faf9;
+  background: #1e3238;
+  font-weight: 700;
+  cursor: pointer;
+}
+
+@media (max-width: 36rem) {
+  .app {
+    width: min(100% - 1rem, 52rem);
+    margin-block: 1rem;
+  }
+
+  .app-header {
+    align-items: stretch;
+    flex-direction: column;
+  }
+
+  .tabs {
+    width: 100%;
+  }
+
+  .reader {
+    border-radius: 0.75rem;
+  }
+
+  .intent-form button {
+    justify-self: stretch;
+  }
 }