One day, Hiro's son, who has reached puberty, accidentally peeks at his parents' sex. More than the shock of seeing his parents act like that, Hiro is shocked that he wanted to do that with his mother, Reika. Since then, Hiro has kept a distance from Reika as if she were in a rebellious period, but the "Assistance Ticket" that Hiro gave Reika when she was young brought the mother and child closer together again. And the filial piety that shows gratitude to his mother gradually turns into obscene filial piety...