"Don't be too violent? Collars hurt when rubbed." The main character, Kurumi, is the daughter of the director of a research facility who secretly conducts outrageous experiments. Among them, she is close in age to the subject called 283 (Tsubasa), and she spends her days taking care of him, who is almost a childhood friend. One day, she had trouble with her facility suddenly losing power. Tsubasa remembers the many experiments that were conducted in the dark and goes on a rampage from the trauma. When she removes her restraints to calm her down, she is drugged and raped by him who is free.