The best LLMs for working in Japanese
English-language reviews rarely test this properly. We judge these models on whether they hold a consistent Japanese register across a long document, handle Japanese proper nouns and industry terms, and can be bought on a Japanese contract with invoice payment.
Published · updated
How we ranked these
Stated before the list, so you can disagree with the weighting rather than the result.
The ranking
- 01
Claude4.9$20/mo
Long-context reasoning with careful, well-structured writing. Strong on drafting, research and design work.
For writing, research and document work — especially in Japanese — this is the first thing to try in 2026. Start on Pro and give yourself a month to judge whether the value is there.
- 02
ChatGPT4.8$20/mo
The default general-purpose assistant: writing, coding help, research and analysis in one place.
The first choice when you want one assistant that does everything. If your work centres on code, long documents or precise Japanese, pair it with Claude rather than replacing it.
- 03
Gemini4.6$20/mo
Google's multimodal assistant, wired natively into Gmail, Docs and Drive.
If Workspace is already deployed across the company, this is the lowest-friction option by a wide margin. As a standalone assistant, ChatGPT and Claude remain stronger.
- 04
Perplexity4.7$20/mo
An answer engine that cites its sources — built for research you have to defend.
The first choice for researchers, writers and consultants who want something better than a search engine. Assume the writing happens elsewhere.
Editors' summary
Four models for Japanese work — official documentation plus our own proofreading passes
| Model | Register | Proper nouns | Long context | Japanese web search | Individual plan |
|---|---|---|---|---|---|
| Claude | Excellent | Good | Excellent — class leading | Limited | $20/moThe 200K-token window is two to four times its competitors. It holds Japanese polite form without drifting, which shows up most clearly in copy and summaries. Native web search integration is limited, so research work usually pairs it with something else. |
| ChatGPT | Good | Excellent — broad multilingual | Good | Excellent — Search built in | $20/moThe widest knowledge of multilingual proper nouns, which means industry terms and personal names come back right more often. ChatGPT Search handles current information natively. In colloquial Japanese it sometimes reads more naturally than Claude. |
| Gemini | Good | Good | Good — very long context | Excellent — Google integration | $19.99/mo, generous free tierThe free tier on a Google account is the most generous of the four, which makes it the easiest entry point. Context length runs into the millions of tokens. Japanese register trails Claude and ChatGPT slightly, offset by how naturally it reaches Workspace content. |
| Perplexity | Limited — search-focused | Good | Limited | Excellent — purpose-built | $20/moBuilt for sourced answers rather than writing. Fastest for look-it-up-and-answer work; for summarising long documents or drafting copy, use one of the others. |
- ※ Excellent = clearly ahead / Good = works in practice / Limited = narrow or situational
- ※ Based on our editorial use for Japanese proofreading, summarisation and long-document work. It will not always agree with public benchmarks such as JGLUE or the Nejumi LLM Leaderboard.
- ※ Individual plan prices are standard rates; the amount you pay varies with tax and exchange rate.
Questions we get
- Which model writes the most natural Japanese?
- For written documents that have to hold a consistent register, Claude. For colloquial text and anything involving many proper nouns, ChatGPT is often better. Most teams that care end up using both.
- Can a Japanese company buy these on a normal contract?
- Yes for all four, though the path differs. Business plans generally support invoice payment and a contract; what varies is whether there is a Japanese entity involved and how data residency is handled. Confirm with the vendor before procurement.
- Is my data used for training?
- On business plans, generally no by default. On individual plans it varies — ChatGPT Plus uses conversations for training unless you turn it off. Check the setting before putting work content into a personal account.
- Do Japanese-developed models belong in this list?
- For general business use the four here remain ahead in practice. Domestically developed models are worth evaluating where data residency inside Japan is a hard requirement; that is a different question from raw capability.