Heiji is bullied by his dodgy senior, Yoneji, and his even senior, Katsuji. One day, Katsuji sees Heiji walking happily with his mother, Miori, and threatens him to bring his mother home. Feeling guilty, Heiji lies to Miori and takes her to the house where the scary seniors are waiting for him... A few days later, his mother doesn't come home and the household is in chaos. Then, when he is called by his senior to go and check on his mother, he finds her in a state of lascivious disarray...