Ryuu Miyazaki

He is actually Riko Asami's older brother.

When their parents got divorced and her mother remarried a man named Yuhei Ishihara, his sister, Riko, was being constantly tortured and beaten. When Riko asked for his help, Ryuu snaps and murdered both his mother and Yuhei Ishihara. He also helped to successfully implement Riko's box 'The Week in the mud'.

After he turned himself in to the police he was sentenced to prison.