According to [https://en.wikipedia.org/wiki/Hepburn_romanization#Syllabic_n], `ちゃっちゃ` should be transliterated as `chatcha`
According to [https://en.wikipedia.org/wiki/Hepburn_romanization#Syllabic_n], `ちゃっちゃ` should be transliterated as `chatcha`

WaniKani/WanaKana,WaniKani/WanaKana