(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

study of history

historic, historical / already-happened, past / former, old, traditional

greedy

(poetic) late autumn; deepest autumn

(colloquial) Clipping of 意味深長 (imishinchō).

Alternative form of 更かす

beneficent / merciful

careful, thoughtful, judicious

deeply sinful