adverb, noun
on the same night; that very night
Used to indicate that something happens on the same night as a previously mentioned event. Often appears in narrative or formal contexts.
彼は到着した即夜、会議に出席した。
He attended the meeting on the same night he arrived.
事件の即夜、警察が現場を調べた。
The police investigated the scene that very night of the incident.