diff --git a/frontend/src/components/TagSearch.test.tsx b/frontend/src/components/TagSearch.test.tsx
new file mode 100644
index 0000000..b66e411
--- /dev/null
+++ b/frontend/src/components/TagSearch.test.tsx
@@ -0,0 +1,120 @@
+import { fireEvent, screen } from '@testing-library/react'
+import userEvent from '@testing-library/user-event'
+import { useLocation } from 'react-router-dom'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+import TagSearch from '@/components/TagSearch'
+import * as api from '@/lib/api'
+import { buildTag } from '@/test/factories'
+import { renderWithProviders } from '@/test/render'
+
+
+const LocationOutput = () => {
+  const location = useLocation ()
+  return <output data-testid="location">{location.pathname}{location.search}</output>
+}
+
+
+const renderSearch = () => renderWithProviders (
+    <>
+      <TagSearch/>
+      <LocationOutput/>
+    </>, { route: '/ja/posts?page=3' })
+
+
+describe ('TagSearch', () => {
+  beforeEach (() => {
+    vi.spyOn (api, 'apiGet').mockResolvedValue ([])
+  })
+
+  it ('searches through native submission without an Enter key event', () => {
+    renderSearch ()
+    const input = screen.getByRole<HTMLInputElement> ('textbox')
+    fireEvent.change (input, { target: { value: '虹夏 not:TEST type:or' } })
+
+    expect (input.form).toBeInstanceOf (HTMLFormElement)
+    fireEvent.submit (input.form!)
+
+    const query = new URLSearchParams ({ tags: '虹夏 not:test', match: 'any' })
+    expect (screen.getByTestId ('location')).toHaveTextContent (
+	`/ja/posts?${ query }`)
+    expect (input).toHaveValue ('虹夏 not:test type:or')
+  })
+
+  it ('requests a search action from the software keyboard', () => {
+    renderSearch ()
+
+    expect (screen.getByRole ('textbox')).toHaveAttribute ('enterkeyhint', 'search')
+  })
+
+  it ('searches through the form when Enter is pressed', async () => {
+    const user = userEvent.setup ()
+    renderSearch ()
+
+    await user.type (screen.getByRole ('textbox'), '虹夏{Enter}')
+
+    const query = new URLSearchParams ({ tags: '虹夏', match: 'all' })
+    expect (screen.getByTestId ('location')).toHaveTextContent (
+	`/ja/posts?${ query }`)
+  })
+
+  it.each ([
+      { label: 'composition flag', composing: true, keyCode: 13 },
+      { label: 'legacy IME code', composing: false, keyCode: 229 }]) (
+      'cancels confirmation Enter with $label', ({ composing, keyCode }) => {
+    renderSearch ()
+    const input = screen.getByRole ('textbox')
+    fireEvent.change (input, { target: { value: '虹夏' } })
+    const uncancelled = fireEvent.keyDown (input, {
+	key: 'Enter', isComposing: composing, keyCode })
+
+    expect (uncancelled).toBe (false)
+    expect (screen.getByTestId ('location')).toHaveTextContent ('/ja/posts?page=3')
+    expect (input).toHaveValue ('虹夏')
+  })
+
+  it ('cancels Enter throughout composition even without keyboard IME flags', () => {
+    renderSearch ()
+    const input = screen.getByRole ('textbox')
+    fireEvent.compositionStart (input)
+    fireEvent.change (input, { target: { value: '虹夏' } })
+    const uncancelled = fireEvent.keyDown (input, {
+	key: 'Enter', isComposing: false, keyCode: 13 })
+
+    expect (uncancelled).toBe (false)
+    expect (screen.getByTestId ('location')).toHaveTextContent ('/ja/posts?page=3')
+    expect (input).toHaveValue ('虹夏')
+  })
+
+  it ('blocks direct submission during composition and allows it after confirmation', () => {
+    renderSearch ()
+    const input = screen.getByRole<HTMLInputElement> ('textbox')
+    fireEvent.compositionStart (input)
+    fireEvent.change (input, { target: { value: '虹夏' } })
+    fireEvent.submit (input.form!)
+
+    expect (screen.getByTestId ('location')).toHaveTextContent ('/ja/posts?page=3')
+    expect (input).toHaveValue ('虹夏')
+
+    fireEvent.compositionEnd (input)
+    fireEvent.submit (input.form!)
+
+    const query = new URLSearchParams ({ tags: '虹夏', match: 'all' })
+    expect (screen.getByTestId ('location')).toHaveTextContent (
+	`/ja/posts?${ query }`)
+  })
+
+  it ('selects the active suggestion without submitting the form', async () => {
+    vi.mocked (api.apiGet).mockResolvedValue ([buildTag ({ name: '虹夏' })])
+    const user = userEvent.setup ()
+    renderSearch ()
+
+    await user.type (screen.getByRole ('textbox'), '虹')
+    await screen.findByText ('虹夏')
+    await user.keyboard ('{ArrowDown}{Enter}')
+
+    expect (screen.getByRole ('textbox')).toHaveValue ('虹夏 ')
+    expect (screen.getByTestId ('location')).toHaveTextContent ('/ja/posts?page=3')
+    expect (screen.queryByText ('虹夏')).not.toBeInTheDocument ()
+  })
+})
diff --git a/frontend/src/components/TagSearch.tsx b/frontend/src/components/TagSearch.tsx
index aa9675f..af5a686 100644
--- a/frontend/src/components/TagSearch.tsx
+++ b/frontend/src/components/TagSearch.tsx
@@ -1,6 +1,6 @@
 // TODO: タグ入力系すべてに同様の処理あるため共通化する．
 
-import { useEffect, useState } from 'react'
+import { useEffect, useRef, useState } from 'react'
 import { useLocation } from 'react-router-dom'
 
 import { useLocale, useLocaleNavigate } from '@/lib/useLocale'
@@ -10,7 +10,7 @@ import { inputClass } from '@/lib/utils'
 
 import TagSearchBox from './TagSearchBox'
 
-import type { ChangeEvent, FC, KeyboardEvent } from 'react'
+import type { ChangeEvent, FC, FormEvent, KeyboardEvent } from 'react'
 
 import type { Tag } from '@/types'
 
@@ -20,6 +20,7 @@ const TagSearch: FC = () => {
   const locale = useLocale ()
   const location = useLocation ()
   const navigate = useLocaleNavigate ()
+  const compositionFlgRef = useRef (false)
 
   const [activeIndex, setActiveIndex] = useState (-1)
   const [search, setSearch] = useState ('')
@@ -74,7 +75,34 @@ const TagSearch: FC = () => {
     setSuggestionsVsbl (false)
   }, [locale])
 
+  const handleSubmit = (ev: FormEvent<HTMLFormElement>) => {
+    ev.preventDefault ()
+    if (compositionFlgRef.current)
+      return
+
+    const parts = search.split (' ')
+    const match =
+	parts.map (t => t.toLowerCase ()).includes ('type:or') ? 'any' : 'all'
+    navigate (`/posts?${
+	(new URLSearchParams ({
+	    tags: parts.map (t => t.toLowerCase ())
+		       .filter (t => t !== 'type:or')
+		       .join (' '),
+	    match })).toString () }`)
+    setSuggestionsVsbl (false)
+    setRequest ({ query: '' })
+  }
+
   const handleKeyDown = (ev: KeyboardEvent<HTMLInputElement>) => {
+    if (compositionFlgRef.current
+	|| ev.nativeEvent.isComposing
+	|| ev.nativeEvent.keyCode === 229)
+    {
+      if (ev.key === 'Enter')
+	ev.preventDefault ()
+      return
+    }
+
     switch (ev.key)
     {
     case 'ArrowDown':
@@ -90,13 +118,12 @@ const TagSearch: FC = () => {
       break
 
     case 'Enter':
-      if (activeIndex < 0)
-	break
-      ev.preventDefault ()
       {
-	const selected = suggestions[activeIndex]
-	if (selected)
-	  handleTagSelect (selected)
+	const selected = suggestionsVsbl ? suggestions[activeIndex] : null
+	if (selected == null)
+	  break
+	ev.preventDefault ()
+	handleTagSelect (selected)
       }
       break
 
@@ -105,20 +132,6 @@ const TagSearch: FC = () => {
       setSuggestionsVsbl (false)
       break
     }
-    if (ev.key === 'Enter' && (!(suggestionsVsbl) || activeIndex < 0))
-      {
-	const parts = search.split (' ')
-	const match = parts.map (t => t.toLowerCase ()).includes ('type:or') ? 'any' : 'all'
-	navigate (`/posts?${
-	    (new URLSearchParams ({
-		tags: parts.map (t => t.toLowerCase ())
-			   .filter (t => t !== 'type:or')
-			   .join (' '),
-		match }))
-	    .toString () }`)
-	setSuggestionsVsbl (false)
-	setRequest ({ query: '' })
-      }
   }
 
   const handleTagSelect = (tag: Tag) => {
@@ -144,8 +157,9 @@ const TagSearch: FC = () => {
   }, [location.search])
 
   return (
-      <div className="relative w-full">
+      <form onSubmit={handleSubmit} className="relative w-full">
 	<input type="text"
+	       enterKeyHint="search"
 	       data-shortcut-focus-search="true"
 	       placeholder={message ('labels.tagSearch').text}
 	       value={search}
@@ -153,12 +167,18 @@ const TagSearch: FC = () => {
 	       onFocus={() => setSuggestionsVsbl (true)}
 	       onBlur={() => setSuggestionsVsbl (false)}
 	       onKeyDown={handleKeyDown}
+	       onCompositionStart={() => {
+		 compositionFlgRef.current = true
+	       }}
+	       onCompositionEnd={() => {
+		 compositionFlgRef.current = false
+	       }}
 	       className={inputClass (false,
 				      'px-3 py-2 dark:border-gray-600 dark:bg-gray-800 dark:text-white')}/>
 	<TagSearchBox suggestions={suggestionsVsbl && suggestions.length ? suggestions : [] as Tag[]}
 		      activeIndex={activeIndex}
 		      onSelect={handleTagSelect}/>
-      </div>)
+      </form>)
 }
 
 export default TagSearch