The line comes from D.Gray-man, the dark-fantasy manga by Katsura Hoshino adapted into an anime series that began airing in 2006. Its main antagonist, the Millennium Earl, habitually greets his victims and his enemies alike with a drawn-out 'konbanwa,' Japanese for 'good evening,' turning a polite greeting into a threat. Fans have long joked about how often he says it, and compilations of every 'konbanwa' circulate online; this clip's metadata traces it to one such Italian-subtitled collection of the Earl's greetings.