Hazama Yoshitomo imprisoned one of his fellow class mates.Her name was Mai. He raped her most likely more than once. He 'got rid of' Mai afterward. Yoshitomo had raped many girls after. He destroyed the phone in the room so she couldn't call the outside world. That's when he left for the door, finding out that the police were at his door.
Yoshitomo lived with his father. His mother was not mentioned so we don't know if she left or died. One day, his father came home late. He had made him dinner. His father brought home a woman, the girl he had already decided on marring. He claimed that she was pregnant with his child and Yoshitomo's sibling.
When the baby boy was born, he was neglected by his father and step-mother. Over the years, it became normal from him. He decided in high school, that he would live one his own in an apartment building.
Yoshitomo went to hang out with a friend from his high school. They go to his house after hang out with other friends. He starts smoking a cigarette while she puts on new layers of lip gloss. They have a conversation about him going home and studying. He claims things are too boring and noisy to go home and study. He gets up and then hugs her from behind. He whispers in her ear, "You will teach me, right?". Yoshitomo then tries to grab her right boob with his left hand, but gets slapped in the process. He plays it off as a joke as they walk to the door. Mai then claims that Yoshitomo only thinks of himself. She then yells "Don't get me caught in your 'Ideal Family Game'!". From this sentence, he gets pissed off and slaps her to the ground. Yoshitomo's mind then starts to race. He thinks he should apologize to Mai for hurting her. "But... It was Mai who hurt my first, right?"
On July 8, he leaves the house and the imprisoned and raped girl all alone. He made a girl breakfast 'as usual'. Yoshitomo claims he is going to school and will be back as soon as possible. Before opening the door, he looks at someone's smashed phone and his home phone. When opening the door, he is greeted by the police.
Because of his crime, his penis was removed, and he was taken to the Institution. Where he meet Yuuki, Kanda, Kengo, Okadai, and the Tezuka twins, Hiza and Hasu.