Kuromi is a white rabbit with a devil's tail and a black hood with a skull, giving her a "cute goth" appearance. She's My Melody's self-proclaimed rival.

Her birthday is 31 October (Halloween). She likes takoyaki and shallots, mischief, and handsome men. Her best friend/minion is Baku the tapir.

She was created by Sanrio in 2005 for the anime Onegai My Melody. In that series, she became a delinquent after countless misfortunes involving My Melody, and uses the Melody Key to corrupt the dreams of humans, hoping to awaken the Dark Power to destroy her.