Aku to Kamen no Rule

Kuki Fumihiro is a son from a wealthy zaibatsu (conglomerate) family. His father raises him to become pure evil. Kuki kills his father to protect his adopted sister Kaori. Afterward, Kuki disappears. He undergoes plastic surgery and takes the identity of Koichi Shintani. He watches Kaori and faces the great evil that exists within the Kuki family