Yoshitoki grew up in an orphanage where he met Shuya Nanahara. One day fed up with his teacher Kitano, Yoshitoki stabbed him in the buttocks during one day of school. Kitano resigned from his position after the incident and Yoshitoki decided to leave school. He only came back after Noriko Nakagawa convinced him by giving him a letter saying come back to school we can go on the class trip together.