One day, his son Hiro, who is in puberty, accidentally peers at his parents' sex. Hiro is even more shocked to see such a thing as her parents, but she is shocked that she wants to do it with her mother, Reika. Since then, Hiro keeps his distance from Reika like he is in a rebellious phase, but the "helping ticket" that Hiro gave Reika when he was a child brings the mother and child closer again. And then, filial piety, expressing gratitude to my mother, gradually transforms into lewd filial piety...