黒歴史

黒 (kuro, “black”) +‎ 歴史 (rekishi, “history”). Originally, this term was used in Turn A Gundam, a Japanese animation, and referred to a fictional past great war.

• IPA^(key): [kɯ̟ᵝɾo̞ɾe̞kʲiɕi]

黒歴史 (hiragana くろれきし, rōmaji kurorekishi)

1. (Internet slang, especially anime and manga fandom) events or things from the past which one wants to whitewash/erase from history (due to it being embarrassing, poorly received, etc.); dark past

• Chinese: 黑歷史／黑历史 (hēilìshǐ)
• Korean: 흑역사 (黑歷史, heugyeoksa)

• なかったこと (nakatta koto)