Chat in English with someone who speaks Japanese

Piou lets you write in English while your contact writes in Japanese: each message is translated on the reader's own device, into their language, and the original is always one tap away. Translation is part of Piou Premium (¥800 a month in Japan, $5.99 in the US, after a 7-day free trial) and keeps working offline once both languages are downloaded.

How it works between English and Japanese

You type in English, your contact types in Japanese, and nobody has to switch. Piou detects the language of each message on the sender's phone and stores it exactly as written. The translation happens on the reader's device: a translated message is labeled “Translated”, and “Show original” reveals the kanji and kana that were actually typed.

No cloud translation service is involved. The engine depends on the device:

• iPhone (iOS 18 or later): Apple's built-in translation.
• Android (8.0 or later): Google's ML Kit, with the language models downloaded to the phone.
• Web app (app.piou.chat): the open-source Bergamot engine with Firefox Translations models, running in the browser, or Chrome's built-in translation on desktop when available. English–Japanese is a direct pair.

Translations never leave the device. The messages themselves are stored on Piou's servers, in their original language, so they can be delivered and synced.

Translation is personal. With Premium, you read everything in English: messages, polls, the text of status updates, and voice messages, which are transcribed and translated while the original audio stays playable. On the free plan, you see the Japanese as written, with a banner once a day per conversation offering to read it in English. Your contact needs Premium to read you in Japanese; if only you have it, Piou suggests gifting it.

An example exchange

Ryan, an American living in Osaka, writes to his mother-in-law, Keiko, about the New Year visit. The translations are illustrative; the exact wording depends on each device's engine.

• Ryan writes: “Hi Keiko! Aya and I would love to visit for New Year's. Can we bring anything?”
  • Keiko reads: “こんにちは、ケイコ！アヤと私はお正月に遊びに行きたいです。何か持っていきましょうか？”
• Keiko writes: “ありがとう。気持ちだけで十分ですよ。二人の元気な顔が見られれば、それで嬉しいです。”
  • Ryan reads: “Thank you. The thought alone is enough. I'll be happy just to see you both doing well.”
• Ryan writes: “Great, see you on the 31st!”
  • Keiko reads: “よかった、では31日に会いましょう！”

Two things are worth noticing. “Hi Keiko” came out as ケイコ, in katakana and without さん: the engine can't know which kanji her name uses, and a bare first name sounds very familiar coming from a son-in-law. Many Japanese sons- and daughters-in-law say お義母さん (“Mother”), so “Hi Mother” is more likely to come out as a respectful お母さん. And Keiko's “the thought alone is enough” is a gracious way of saying “don't bring anything”; even so, many people still bring a small gift when visiting family.

Tips for writing to Japanese speakers

• Add -san. Outside family and close friends, people in Japan usually address each other by family name plus さん (Tanaka-san). Writing “Ms. Tanaka” or “Tanaka-san” helps keep that respect in the translation.
• Make the subject explicit. “I'll send it tomorrow” translates better than “Will send tomorrow.” Short, complete sentences come through most reliably.
• Listen for the soft no. ちょっと難しいです (“that's a little difficult”) or 検討します (“we'll consider it”) often means no. The translation is accurate word for word, which is exactly why the meaning can slip by.
• Read すみません in context. It can mean “sorry”, “excuse me” or “thank you for the trouble”. An apology in the translation isn't always an admission of fault.
• Check the year. Japanese writes dates year, month, day, and official documents often use the Japanese era system: Reiwa 8 (令和8年) is 2026.
• Count in ten-thousands. Large numbers are grouped by 万 (10,000), so 3万円 is ¥30,000. Restate important amounts in figures.

Translation limits to know

• Keigo flattened. Japanese moves between casual speech, polite です/ます forms and honorific or humble keigo. English has no equivalent, so a carefully respectful message reads as plain English, and in the other direction the engine chooses a level that may not fit your relationship.
• Hidden subjects. Japanese often omits “I”, “you” or “we”, so the engine guesses who is doing what.
• Names. The engine can't know which kanji a name uses and may write it in katakana. Names that are also words, such as 誠 (Makoto, “sincerity”) or 春 (Haru, “spring”), may be translated as words.
• Katakana English. Some loanwords shifted meaning in Japanese: マンション is an apartment building, not a mansion, and テンションが高い means “in high spirits”, not “tense”. These can be mistranslated.
• Internet slang. w or 草 for laughter and contractions like りょ (“got it”) may come through untranslated.
• Voice. Transcription, subtitles and Face to face mode depend on what your device's speech recognition supports; strong regional accents or background noise lower accuracy.
• High stakes. For medical, legal, immigration, money or contract questions, rely on a professional interpreter or a human translation. In an emergency in Japan, call 119 for an ambulance or fire, and 110 for the police.

Getting started

1. Install Piou on an iPhone (iOS 18 or later) or an Android phone (8.0 or later), or open app.piou.chat and add it to your home screen (Safari → Share → “Add to Home Screen” on iPhone; Chrome → ⋮ → “Install app” on Android).
2. Create your account with Apple, Google or an email address, choose English, and verify your phone number once. It lets your contacts find you; it's never used to sign in.
3. Download English and Japanese on Wi-Fi so translation also works offline.
4. Add your contact from “Already on Piou”, or send an invite link or QR code. They choose Japanese as their language.
5. Start the 7-day free trial. A card is required and nothing is charged for 7 days. If you want your contact to read you in Japanese, tap “Gift Piou to someone”.