Loek van Kooten, MAGPT-4o scored 0.29 accuracy on Japanese negative questions; a core politeness structure in the language.
You probably can't read Japanese, so let me show you what that feels like in English. Imagine every message in your game (every tutorial prompt, every NPC greeting, every support page) stripped of all courtesy. Technically correct. Culturally dead. "Thank you for your purchase! We hope you enjoy the adventure. " becomes "You bought it. Play. " "We sincerely apologize for the inconvenience. " becomes "Bug. Wait. " That's what AI does to Japanese keigo.
It flattens the politeness system that governs every interaction in the language. DeepL often flattened keigo into generic politeness, requiring post-editing. Claude tended to over-soften. And GPT-4o needs very specific prompting to avoid mangling politeness levels entirely. Their bottom line: "For Japanese localization, AI output should be treated as draft quality. " Your English-speaking players would never accept a game that talks to them like this. Why should your Japanese players?
Source: Ulatus, "2026 Japanese-to-English AI Translator Shootout: GPT-4o vs DeepL vs Claude on Keigo, Subtext, and Brand Voice," January 2026 #GameLocalization #Japanese #Localization #AI #Keigo #GameDev #CJK #Translation