If you write business email or documents in Japanese as a non-native speaker, the part that breaks isn't grammar — it's keigo, the honorific register. This guide explains what keigo is, why generic translators get it wrong, and what to look for in a keigo translator built for business writing.
What keigo actually is
Keigo is the system Japanese uses to encode social relationships directly into verbs, nouns, and sentence endings. Three forms:
- Teineigo (polite): the safe middle register.desu / masu endings. Use with peers and casual business contacts.
- Sonkeigo (respectful): used when describing the actions of someone you're respecting — your boss, your customer. Verbs change: miru (to see) becomes goran ni naru.
- Kenjogo (humble): used when describing your own actions to indirectly elevate the other party. miru becomes haiken suru.
Two sentences with identical literal meanings can use entirely different forms depending on who you're writing to. That's why translating English to Japanese with a generic tool produces Japanese that's grammatically correct but socially wrong.
Why Google / DeepL get keigo wrong
Generic translators optimise for the median — the most likely translation a typical sentence needs. The median in Japanese business writing is teineigo: polite but not deferential. That's fine for internal email between peers. It's too weak for:
- Emails to clients you haven't met
- Apology emails after a mistake
- Requests to senior contacts
- Anything where you'd say "if it's not too much trouble" in English
It's also too strong for casual internal Slack-like messages, where the same heavy keigo reads as cold or sarcastic.
The three things a real keigo translator does
1. Asks who you're writing to
BizHonyaku and similar business-specific tools expose a dropdown: peer / manager / external client / first-contact / executive. The same English sentence translates differently for each. Generic tools force you to encode this in a prompt or accept the median.
2. Catches double-honorifics
Overshooting is as bad as undershooting. Generic translators sometimes stack two humble verbs (ご確認頂戴いたします) which native readers immediately read as broken. A keigo-aware translator detects and rewrites these.
3. Respects cushion phrases
Japanese business writing pads requests with formulaic softeners: お忙しいところ恐縮ですが ("sorry to bother you when you're busy"), 誠に勝手ながら ("with all due deference"). These aren't decorative — they're structural. A keigo translator inserts them when the situation calls for them.
Concrete example
English source: Please review the contract and let us know your thoughts.
Generic translator output:
契約書を確認して、ご意見をお知らせください。
Grammatically correct. Tone reads as instruction to a subordinate. Inappropriate for a client.
Keigo translator (external client setting):
お忙しいところ恐縮ですが、契約書をご確認のうえ、ご意見をお聞かせいただけますと幸いです。
Cushion phrase ("sorry to bother you"), kenjogo ("ご確認"), polite request form ("いただけますと幸いです"). Same literal meaning, completely different social register.
When you still want a human
AI keigo translation is now good enough for daily business writing — email, reports, internal documents, marketing copy. It still struggles with:
- Senior-leadership communication where every word matters
- Legal contracts with binding language
- High-stakes apologies (resignation, customer escalation)
For those, draft with AI and have a native bilingual reviewer pass before sending. The AI saves 80% of the time; the review catches the 5% of cases where the register is off by one notch.
Trying BizHonyaku
BizHonyaku is a business-document AI translator with keigo dropdowns, double-honorific detection, and the cushion-phrase logic above. EN ↔ JP, Word / PDF / Excel / PowerPoint, with five free translations per month so you can test it on real work before paying. If you're writing Japanese business email regularly and using a generic tool, the difference shows in the first email.