You Takami

A kleptomaniac and an informant to Assistant Warden Tamaki Yoh was hired to watch over Ganta in return of large amounts for Cast Points. Though apparently friendly and polite in truth he is ruthless scheming and somehow paranoid given his position as a spy for the prisons staff. A rarity among the prison population Yoh made himself captured and sent to Deadman Wonderland in hopes to find his sister Minatsuki and buy her freedom with the accumulated Cast Points he got from Tamaki. He cares deeply about her so much so that he is often thought of suffering from a sister complex much to Minatsukis disgust. The two eventually manage to forge an estranged relationship. Wikipedia