Izumi is a sadistic bully, everyone and everything is a plaything to her. She is overconfident in her ability to withstand hypnosis which leads her to be hypnotized in the first place.
After she is hypnotized, she has sex countless times with Tazaki, as he implanted the notion that being raped by a girl he doesn't love would be torture for him. Izumi also intended to get pregnant with his baby. Tazaki created another rule where every time he would ejaculate inside her, she would feel intense love towards the baby inside her, that would give her euphoria. Ultimately, he would use the hypnosis to fix her terrible personality and become loyal to him.
