diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index d3a39cd3..42274836 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -29,14 +29,17 @@ model Locale {
 }
 
 model Text {
-  id          Int      @id @default(autoincrement())
-  created_at  DateTime @default(now())
-  updated_at  DateTime @updatedAt
-  language_id Int
-  text        String   
-  language    Language @relation(fields: [language_id], references: [id])
+  id          Int          @id @default(autoincrement())
+  created_at  DateTime     @default(now())
+  updated_at  DateTime     @updatedAt
+  language_id Int          
+  text        String
+  language    Language     @relation(fields: [language_id], references: [id])
+  TextToText1 TextToText[] @relation("TextToText1")
+  TextToText2 TextToText[] @relation("TextToText2")
 
   @@unique([language_id, text])
+  @@index([language_id])
 }
 
 model Sound {
@@ -44,8 +47,22 @@ model Sound {
   created_at DateTime @default(now())
   updated_at DateTime @updatedAt
   locale_id  Int
-  sound_text String   
+  sound_text String
   locale     Locale   @relation(fields: [locale_id], references: [id])
 
   @@unique([locale_id, sound_text])
 }
+
+model TextToText {
+  id         Int      @id @default(autoincrement())
+  created_at DateTime @default(now())
+  updated_at DateTime @updatedAt
+  text_id_1  Int
+  text_id_2  Int
+  text_1     Text     @relation(name: "TextToText1", fields: [text_id_1], references: [id])
+  text_2     Text     @relation(name: "TextToText2", fields: [text_id_2], references: [id])
+
+  @@unique([text_id_1, text_id_2])
+  @@index([text_id_1])
+  @@index([text_id_2])
+}
diff --git a/src/lib/api.ts b/src/lib/api.ts
index 20d0a6ab..a77e0d4d 100644
--- a/src/lib/api.ts
+++ b/src/lib/api.ts
@@ -41,10 +41,21 @@ export class Api {
 		return result
 	}
 
-	public async add_text(text: string, language_code: string): Promise<Text> {
-		return await this._fetch<Text>(`/api/add-text/${text}/${language_code}`)
+	public async add_text(language_code: string, text: string): Promise<Text> {
+		return await this._fetch<Text>(`/api/add-text/${language_code}/${text}`)
 	}
 
+	public async add_translation(text_id: number, language_to_code: string, translation: string): Promise<Text> {
+		return await this._fetch<Text>(
+			`/api/add-translation/${text_id}/${language_to_code}/${translation}`
+		)
+	}
+
+	public async find_translation(text_id: number, language_to_code: string): Promise<Text[]> {
+		return await this._fetch<Text[]>(`/api/find-translation/${text_id}/${language_to_code}`)
+	}
+
+
 	// HACK: 結合方法不明のため保留
 	// async function split_sentences(text: string, url: URL): Promise<string[]> {
 	// 	const split_response = await fetch(`${url.origin}/api/split-sentence/${text}`)
diff --git a/src/lib/database.ts b/src/lib/database.ts
index 9acc9cc7..8aedcf84 100644
--- a/src/lib/database.ts
+++ b/src/lib/database.ts
@@ -3,12 +3,15 @@ import { PrismaClient, type Language, type Locale, type Sound, type Text } from
 export const db = new PrismaClient()
 export class Database {
 	public static async get_texts(language_code: string): Promise<Text[]> {
-		const texts = await db.text.findMany({ where: { language: { code: language_code } }, orderBy: { updated_at: 'desc' } })
+		const texts = await db.text.findMany({
+			where: { language: { code: language_code } },
+			orderBy: { updated_at: 'desc' },
+		})
 
 		return texts
 	}
 
-	public static async sound_upsert(sound_text: string, locale_code: string): Promise<Sound> {
+	public static async sound_upsert(locale_code: string, sound_text: string): Promise<Sound> {
 		const locale = await db.locale.findUnique({ where: { code: locale_code } })
 
 		if (!locale) throw new Error('locale not found')
@@ -52,8 +55,20 @@ export class Database {
 		return locales
 	}
 
-	public static async text_upsert(text: string, language_code: string): Promise<Text> {
-		const language = await db.language.findUnique({ where: { code: language_code } })
+	public static async language_find_by_code(code: string): Promise<Language | null> {
+		const language = await db.language.findUnique({ where: { code } })
+
+		return language
+	}
+
+	public static async text_find_by_id(id: number): Promise<Text | null> {
+		const text = await db.text.findUnique({ where: { id } })
+
+		return text
+	}
+
+	public static async text_upsert(language_code: string, text: string): Promise<Text> {
+		const language = await this.language_find_by_code(language_code)
 
 		if (!language) throw new Error('language not found')
 
@@ -72,4 +87,72 @@ export class Database {
 
 		return result
 	}
+
+	public static async find_translation(
+		text_id: number,
+		language_code: string
+	): Promise<Text[]> {
+		const text = await this.text_find_by_id(text_id)
+		const language = await this.language_find_by_code(language_code)
+
+		if (!text) throw new Error('text not found')
+		if (!language) throw new Error('language not found')
+
+		const text_ids: number[] = []
+
+		const translation_to = await db.textToText.findMany({
+			where: {
+				text_id_1: text_id,
+				text_2: { language_id: language.id },
+			},
+		})
+
+		translation_to.forEach((t) => text_ids.push(t.text_id_2))
+
+		const translation_from = await db.textToText.findMany({
+			where: {
+				text_id_2: text_id,
+				text_1: { language_id: language.id },
+			},
+		})
+
+		translation_from.forEach((t) => text_ids.push(t.text_id_1))
+
+		const texts = await db.text.findMany({
+			where: {
+				id: {
+					in: text_ids,
+				},
+			},
+			orderBy: { updated_at: 'desc' },
+		})
+
+		return texts
+	}
+
+	public static async add_translation(text_id: number, language_code: string, translation: string): Promise<Text> {
+		const text = await this.text_find_by_id(text_id)
+		const language = await this.language_find_by_code(language_code)
+
+		if (!text) throw new Error('text not found')
+		if (!language) throw new Error('language not found')
+
+		const translation_text = await this.text_upsert(language_code, translation)
+
+		await db.textToText.upsert({
+			where: {
+				text_id_1_text_id_2: {
+					text_id_1: text.id,
+					text_id_2: translation_text.id,
+				},
+			},
+			update: {},
+			create: {
+				text_id_1: text.id,
+				text_id_2: translation_text.id,
+			},
+		})
+
+		return translation_text
+	}
 }
diff --git a/src/routes/+page.svelte b/src/routes/+page.svelte
index 762d5cc2..cafb9455 100644
--- a/src/routes/+page.svelte
+++ b/src/routes/+page.svelte
@@ -23,11 +23,12 @@
 	let audio_element: HTMLAudioElement
 
 	let texts: Text[] = []
-	let selected_text = ''
-	let translated_text = ''
+	let selected_text: Text | undefined
+	let translations: string[] = []
 	let language_from_code = ''
 	let locale_code = ''
 	let language_to_code = ''
+	let add_translation_string = ''
 
 	function init_language_select(): void {
 		const languages = JSON.parse(data.languages) as Language[]
@@ -53,7 +54,7 @@
 
 		const locales = JSON.parse(data.locales) as Locale[]
 
-		selected_text = ''
+		selected_text = undefined
 
 		Html.append_locale_select_options(locale_select_element, locales, language_from_code)
 		on_change_locale_select(store_language)
@@ -84,7 +85,7 @@
 	}
 
 	function on_change_locale_select(store_locale = true): void {
-		console.log('on_change_locale_select')
+		// console.log('on_change_locale_select')
 
 		if (!store_locale) {
 			const locale = localStorage.getItem('locale')
@@ -98,16 +99,16 @@
 		}
 	}
 
-	function on_click_text(text: string): void {
+	function on_click_text(text: Text): void {
 		// const language_code =
 		// 	from_language_select.selectedOptions[0].getAttribute('language_code') ?? ''
 
 		if (text === selected_text) {
-			console.log('same text')
+			// console.log('same text')
 			audio_element.play()
 		} else {
 			selected_text = text
-			translated_text = ''
+			translations = []
 		}
 
 		// const voice_name = language_code === 'ja-JP' ? 'Google 日本語' : 'Google US English'
@@ -115,26 +116,60 @@
 		// speech(selected_text, language_code, voice_name)
 	}
 
-	function add_translation(): void {
-		// TODO:
+	async function find_translation(): Promise<string[]> {
+		if (!selected_text) return []
+
+		const translation_texts = await new Api().find_translation(selected_text.id, language_to_code)
+		const translations = translation_texts.map((translation_text) => translation_text.text)
+
+		return translations
 	}
 
 	async function show_translation(): Promise<void> {
 		if (language_from_code === language_to_code) {
-			translated_text = `(${$_('select_different_language')})`
+			translations = [(`(${$_('select_different_language')})`)]
 			return
 		}
 
 		if (!selected_text) {
-			translated_text = `(${$_('select_text_first')})`
+			translations = [(`(${$_('select_text_first')})`)]
 			return
 		}
 
-		translated_text = await new Api().translate_by_google(selected_text, language_to_code)
+		const find_translation_result = await find_translation()
+
+		if (find_translation_result.length > 0) {
+			translations = find_translation_result
+			// console.info('translations found.', translations)
+		} else {
+			const translation = await new Api().translate_by_google(selected_text.text, language_to_code)
+			
+			await new Api().add_translation(selected_text.id, language_to_code, translation)
+			
+			translations = await find_translation()
+			// console.info('translated', translation)
+		}
+	}
+
+	async function add_translation(): Promise<void> {
+		if (!selected_text) return
+		if (!add_translation_string) return
+
+		// console.log('add_translation', selected_text)
+		// console.log('language_to_code', language_to_code)
+
+		await new Api().add_translation(selected_text.id, language_to_code, add_translation_string)
+
+		add_translation_string = ''
+
+		await show_translation()
+		// TODO: 選択されているテキストを探す
+		// TODO: 翻訳を登録する
+		// TODO: 選択されているテキストと翻訳を関連付ける
 	}
 
 	function init(): void {
-		translated_text = ''
+		translations = []
 		speech_text_element.textContent = `(${$_('lets_talk')})`
 	}
 
@@ -151,7 +186,7 @@
 
 		if (!new_text_element.value) return
 
-		await new Api().add_text(new_text_element.value, language_from_code)
+		await new Api().add_text(language_from_code, new_text_element.value)
 
 		// console.info('add_text', text)
 
@@ -205,7 +240,7 @@
 				{#each texts as text}
 					<div
 						class="padding_10px_16px cursor_pointer hover"
-						on:click={() => on_click_text(text.text)}
+						on:click={() => on_click_text(text)}
 						on:keydown
 					>
 						{text.text}
@@ -217,7 +252,7 @@
 		<div class="footer flex_column gap_16px">
 			<div>
 				<audio
-					src={new Api().get_speech_to_text_url(selected_text, locale_code)}
+					src={new Api().get_speech_to_text_url(selected_text?.text ?? '', locale_code)}
 					controls
 					autoplay
 					bind:this={audio_element}
@@ -250,11 +285,16 @@
 						lang={Lang.to_text_language_code(language_to_code)}
 						class="flex_1 overflow_wrap_anywhere"
 					>
-						{translated_text}
+						{@html translations.join('<br />')}
 					</div>
 				</div>
 				<div class="flex_row gap_8px align_items_center">
-					<input type="text" class="flex_1" placeholder={$_('enter_new_translation')} />
+					<input
+						type="text"
+						class="flex_1"
+						placeholder={$_('enter_new_translation')}
+						bind:value={add_translation_string}
+					/>
 					<button on:click={add_translation}>
 						<div class="flex_row justify_content_center height_24px"><AddIcon /></div>
 					</button>
diff --git a/src/routes/api/add-text/[text]/[language_code]/+server.ts b/src/routes/api/add-text/[language_code]/[text]/+server.ts
similarity index 82%
rename from src/routes/api/add-text/[text]/[language_code]/+server.ts
rename to src/routes/api/add-text/[language_code]/[text]/+server.ts
index da1f461c..4214ca78 100644
--- a/src/routes/api/add-text/[text]/[language_code]/+server.ts
+++ b/src/routes/api/add-text/[language_code]/[text]/+server.ts
@@ -1,24 +1,21 @@
 import { Database } from '$lib/database'
 import { json, type RequestHandler } from '@sveltejs/kit'
 
-
-
 export const GET: RequestHandler = async ({ url, params }) => {
-	console.log(url.href)
+	console.info(url.href)
 
-	const text = (params.text ?? '').trim()
 	const language_code = (params.language_code ?? '').trim()
+	const text = (params.text ?? '').trim()
 
 	if (text === '' || language_code === '') {
 		return new Response('text or language_code is empty', { status: 400 })
 	}
 
 	try {
-		const result = await Database.text_upsert(text, language_code)
+		const result = await Database.text_upsert(language_code, text)
 
 		return json(result)
-	}
-	catch (e) {
+	} catch (e) {
 		console.error(e)
 		return new Response((e as Error).message, { status: 400 })
 	}
diff --git a/src/routes/api/add-translation/[text_id]/[language_code]/[translation]/+server.ts b/src/routes/api/add-translation/[text_id]/[language_code]/[translation]/+server.ts
new file mode 100644
index 00000000..f89e1ff9
--- /dev/null
+++ b/src/routes/api/add-translation/[text_id]/[language_code]/[translation]/+server.ts
@@ -0,0 +1,23 @@
+import { Database } from '$lib/database'
+import { json, type RequestHandler } from '@sveltejs/kit'
+
+export const GET: RequestHandler = async ({ url, params }) => {
+	console.info(url.href)
+
+	const text_id = Number((params.text_id ?? '').trim())
+	const language_code = (params.language_code ?? '').trim()
+	const translation = (params.translation ?? '').trim()
+
+	if (isNaN(text_id) || language_code === '' || translation === '') {
+		return new Response('text_id or language_to_code is empty', { status: 400 })
+	}
+
+	try {
+		const result = await Database.add_translation(text_id, language_code, translation)
+
+		return json(result)
+	} catch (e) {
+		console.error(e)
+		return new Response((e as Error).message, { status: 400 })
+	}
+}
diff --git a/src/routes/api/find-translation/[text_id]/[language_code]/+server.ts b/src/routes/api/find-translation/[text_id]/[language_code]/+server.ts
new file mode 100644
index 00000000..ae61d751
--- /dev/null
+++ b/src/routes/api/find-translation/[text_id]/[language_code]/+server.ts
@@ -0,0 +1,22 @@
+import { Database } from '$lib/database'
+import { json, type RequestHandler } from '@sveltejs/kit'
+
+export const GET: RequestHandler = async ({ url, params }) => {
+	console.info(url.href)
+
+	const text_id = Number((params.text_id ?? '').trim())
+	const language_code = (params.language_code ?? '').trim()
+
+	if (isNaN(text_id) || language_code === '') {
+		return new Response('text_id or language_to_code is empty', { status: 400 })
+	}
+
+	try {
+		const result = await Database.find_translation(text_id, language_code)
+
+		return json(result)
+	} catch (e) {
+		console.error(e)
+		return new Response((e as Error).message, { status: 400 })
+	}
+}
diff --git a/src/routes/api/text-to-speech/[text]/[locale_code]/+server.ts b/src/routes/api/text-to-speech/[text]/[locale_code]/+server.ts
index e687eda3..40828187 100644
--- a/src/routes/api/text-to-speech/[text]/[locale_code]/+server.ts
+++ b/src/routes/api/text-to-speech/[text]/[locale_code]/+server.ts
@@ -23,7 +23,7 @@ async function get_buffers(sentences: string[], locale_code: string): Promise<Bu
 		}
 
 		const audio_content = (await GoogleSpeech.synthesize_speech(sentence, locale_code)) as Buffer
-		const {id: sound_id} = await Database.sound_upsert(sentence, locale_code)
+		const { id: sound_id } = await Database.sound_upsert(locale_code, sentence)
 
 		File.write_sound(sound_id, audio_content)
 		console.info(`Created #${sound_id} sound for "${sentence}"`)
@@ -34,7 +34,7 @@ async function get_buffers(sentences: string[], locale_code: string): Promise<Bu
 }
 
 export const GET: RequestHandler = async ({ url, params }) => {
-	console.log(url.href)
+	console.info(url.href)
 
 	const text = params.text ?? ''
 	const locale_code = params.locale_code ?? ''
diff --git a/src/routes/api/translate-by-google/[text]/[target_lang]/+server.ts b/src/routes/api/translate-by-google/[text]/[target_lang]/+server.ts
index 5e02d946..e21739f7 100644
--- a/src/routes/api/translate-by-google/[text]/[target_lang]/+server.ts
+++ b/src/routes/api/translate-by-google/[text]/[target_lang]/+server.ts
@@ -4,7 +4,7 @@ import { json, type RequestHandler } from "@sveltejs/kit";
 
 
 export const GET: RequestHandler = async ({ url, params }) => {
-	console.log(url.href)
+	console.info(url.href)
 
 	const trimmed_text = params.text?.trim() ?? ''
 	const target_lang = params.target_lang?.trim() ?? 'en'
@@ -15,7 +15,7 @@ export const GET: RequestHandler = async ({ url, params }) => {
 	const translate = new Translate()
 	const [translations] = await translate.translate(trimmed_text, target_lang2)
 
-	console.log(translations)
+	// console.log(translations)
 
 	return json(translations)
 }
\ No newline at end of file
diff --git a/src/routes/api/translate_by_deepl/[text]/[target_lang]/+server.ts b/src/routes/api/translate_by_deepl/[text]/[target_lang]/+server.ts
index 3fd57efb..ee71933a 100644
--- a/src/routes/api/translate_by_deepl/[text]/[target_lang]/+server.ts
+++ b/src/routes/api/translate_by_deepl/[text]/[target_lang]/+server.ts
@@ -4,7 +4,7 @@ import { json, type RequestHandler } from '@sveltejs/kit'
 import type { TargetLanguageCode } from 'deepl-node'
 
 export const GET: RequestHandler = async ({ url, params }) => {
-	console.log(url.href)
+	console.info(url.href)
 
 	const trimmed_text = params.text?.trim() ?? ''
 	// TODO: Translate to selected language #77