A female student, Reina, visits the home of her shut-in classmate, Masao. However, when she presses the intercom, no one answers. Just as she is about to give up on an errand she was given by her teacher and head home, a man named Koji appears. Koji introduces himself as Masao's father and calls his son a "bad brat." Enraged by his words, Reina ignores Koji's pleas to stop her and enters Masao's room. As soon as Masao sees Reina, he pins her down. Then the guys in the room and Koji join in...