The laugh comes from Death Note, the anime adaptation of the manga about Light Yagami, a student who gains a notebook that kills anyone whose name he writes in it and adopts the alias Kira. In the Japanese dub, Light's laughter became one of the series' most quoted moments, shared widely in anime edits, reaction videos and short-form memes. Years later it remains popular because it instantly signals arrogance, madness and a plan coming together, even for viewers who have never watched the full series.