Video Description: One late night, when Rei Mizuna was going home from her teaching job, one of her students was waiting for her in front of her building. He confessed that he was afraid to go home because of his bad grades. And he asked for some help. The teacher agreed to help him and invited him to her apartment. After a bit of studying, when she left him alone to finish some of her work, the student got up, unlocked the door, and let three of his friends in the apartment.