Nihei Hikaru

He looks down upon his inept classmates. He started attending cram school from an early age and earns the best grades. He began to look down upon his peers more and more as time went on. Eventually, he ended up picking on one of his classmates for being "an underachiever". He was bullied because of that, and so he channelled his anger through attacking rabbits. He's slightly mental. He hides a twisted split personality within the darkness of his own mind.

One day, an unranked youkai named Hameln reveals that he has been watching Hikaru abuse the rabbits. Seeing Hikaru as an opportunity, Hameln uses Hikaru in order to achieve his goal of becoming a ranked youkai. Hameln's castanets (when played in the music room) has the power to turn those who hear its tune into small animals. Feigning cooperation, Hameln turned Hikaru's "tormentors" into rabbits, and then Hikaru would slaughter them.