Using AI in a language other than English costs more tokens for the same content. Even among the 20 most common languages, the gap is up to 5x.
Japanese grammar is already complex, and keigo (polite speech) adds more. A polite request took 29 tokens; “要約して。” (“summarize it”) took 10 (measured with GPT’s tokenizer).
You don’t need keigo with AI. It’s cheaper, and the answers get more concise.