Minori is incarcerated at a women's medical prison exclusively for inmates with mental and physical disabilities. She was incarcerated for manslaughter, but in fact she deliberately entered the prison to investigate the mysterious suicide of her younger sister, Manami, who was also incarcerated there two years prior. Although billed as a rehabilitation support facility, the prison has in reality become a testing ground for guards who repeatedly assault female inmates, and for the warden and in-house doctor to conduct personality reform experiments.