Using AI for Japanese: Prompts That Force Keigo or Casual Mode

Hi everyone! Kenji here 😊

If you study Japanese and don't have someone to practice with, AI chatbots (ChatGPT, Claude, Gemini) can fill the gap — but only if you tell them exactly what register you want. Without specific framing, they default to a vaguely polite middle ground that doesn't help you master either 敬語けいご (keigo, formal) or 溜ため口ぐち (tameguchi, casual).

Let me share the prompt formulas that actually work.

👔 Making AI a 'strict department head' (keigo mode)

Keigo isn't just adding ~です/ます. It splits into 尊敬語そんけいご (respectful — for the listener's actions) and 謙譲語けんじょうご (humble — for your own actions).

The key trick: give the AI a specific persona, not just a role.

💡 Tip: Don't say 'be a Japanese teacher'. Say 'be a 30-year-veteran department head at a Tokyo trading firm who's strict but polite'. The detail makes the AI's tone feel authentic.

Keigo practice prompt template

📝 Business-keigo roleplay prompt

"You are the 部長ぶちょう (department head) of a Japanese IT company. I am a new hire on my first day. We're meeting in the conference room for the first time. You'll give me work instructions, and I must respond using full keigo. After our dialogue ends, please flag any natural-sounding errors in my Japanese in a [Corrections] section at the bottom."

📖 Business phrases the AI should elicit

Situation	Phrase	Meaning
First meeting	初はじめまして	Nice to meet you
Asking for favor	宜よろしくお願ねがいいたします	Please look after me
Excusing yourself	失礼しつれいいたします	Excuse me
Acknowledging an instruction	承知しょうちいたしました	Understood / will comply

🍻 Making AI a 'close friend' (tameguchi mode)

Many learners assume tameguchi = strip the polite endings off keigo. Not quite. Casual Japanese has its own grammar — different particles (の at sentence-end, よね for empathy), contractions (~てる, ~ちゃう, ~なきゃ), and rhythm.

The AI defaults to overly-polite Japanese. Push back explicitly.

Casual practice prompt template

📝 Friend-mode roleplay prompt

"You are my 10-years-since-college Japanese friend. We're at an izakaya in Shibuya drinking beer. The vibe is super relaxed and fun — use full tameguchi, slang, and contractions naturally. Drop in some trending words. Don't be too rough — keep it warm friend-mode."

⚠️ Specify warm friend mode — without that guardrail, the AI might over-correct and produce overly-crude language with too many ぞ/ぜ/だっつーの.

📊 What 'friend Japanese' actually looks like

Vs. keigo equivalents:

Situation Keigo Tameguchi
Where are you going? 明日あした、どこに行いかれますか？明日あした、どこ行いくの？
I want to go 行いきたいです行いきたい
I understood 承知しょうちいたしましたわかった / 了解りょうかい
Sorry 申もうし訳わけありませんごめん

Situation	Keigo	Tameguchi
Where are you going?	明日あした、どこに行いかれますか？	明日あした、どこ行いくの？
I want to go	行いきたいです	行いきたい
I understood	承知しょうちいたしました	わかった / 了解りょうかい
Sorry	申もうし訳わけありません	ごめん

🛠️ Bonus: how to ask the AI to correct you mid-conversation

The best prompt addition I've found: tell the AI to keep dialogue flowing AND list corrections at the end.

📝 Corrections add-on

"Keep the dialogue going naturally — don't interrupt to correct me. After my response, in a [Corrections] block at the bottom, flag any phrases that sounded unnatural and rewrite them properly."

This gives you the immersion of conversation + the feedback of a tutor in one go.

✨ Kenji's recap

Set a specific persona (job + setting + relationship), not a generic role.
Force keigo mode with strict boss + new hire + first day scenarios.
Force tameguchi mode with close friend + casual venue + warm vibe.
Ask for [Corrections] block at the end so you can keep flow + still learn.
AI cannot replace humans — but it can fill 80% of practice time when no humans are available.

Give it a try with one of the templates. Three days later your Japanese will feel sharper. 🎯