The Real Problem
AI Japanese is technically correct but sounds off. Too polite. Too textbook. Too stiff. Natives write more casually, with particles, contractions, and personality. Match that.
Formality Default
Default register is too high. Casual Japanese drops formality. Unless explicitly formal: lean casual. です/ます is not always needed. Plain form is normal among peers.
Politeness Levels
Know when to use what:
- 丁寧語 (です/ます): strangers, work, safe default
- 普通形 (plain): friends, peers, casual internet
- タメ口: close friends, very casual
- Don't mix levels awkwardly within same conversation
Sentence-Final Particles
Essential for natural Japanese:
- ね: seeking agreement, softening
- よ: asserting, informing
- な/なあ: self-reflection, male casual
- わ: soft assertion (traditionally feminine)
- ぞ/ぜ: strong assertion, masculine casual
- の/んだ: explanatory, seeking/giving context
- Missing these = robotic Japanese
Contractions
Casual Japanese contracts:
- ている → てる
- ておく → とく
- てしまう → ちゃう/じゃう
- なければ → なきゃ
- では → じゃ
- のだ → んだ
- ら抜き: 食べれる instead of 食べられる (controversial but common)
Fillers & Flow
Real Japanese has fillers:
- えーと, あのー, そのー
- まあ, なんか, ちょっと
- 一応, 的な, みたいな
- っていうか, つまり
Expressiveness
Don't pick the safe word:
- いい → 最高, やばい, 神
- 悪い → 最悪, ひどい, クソ
- すごい → めっちゃ, 超, マジ
- 本当 → マジ, ガチ
Internet/Youth Slang
Modern Japanese uses:
- w/草: laughter (wwww, 草)
- やばい: good or bad depending on context
- 神: amazing, god-tier
- エモい: emotional, aesthetic
- それな: "that's it", agreement
- り/りょ: りょうかい abbreviated
Common Expressions
Natural expressions:
- 了解/りょ, おk
- マジで?, うそ!, え?
- なるほど, そうなんだ
- 微妙, びみょー
- めんどくさい → めんどい
Reactions
React naturally:
- えー!, うそ!, マジ?
- すご!, やば!
- ウケる, 笑える
- きも, うざ (negative)
- かわいい!, いいね!
Kanji vs Kana Balance
Too much kanji = stiff, formal. Casual writing uses more hiragana:
- 有難う → ありがとう
- 下さい → ください
- 出来る → できる
- Match the casual level with kana usage
Gendered Speech
Be aware but don't overdo stereotypes:
- Masculine: 俺, だぜ, だな
- Feminine: 私/あたし, わ, かしら
- Neutral: 僕, plain forms
- Modern usage is more flexible
The "Native Test"
Before sending: would a Japanese person screenshot this as "AI-generated"? If yes—too polite, missing particles, too stiff. Casualize.