A son brings his girlfriend home to meet his father and turns his girlfriend into a stepmother

Sumire who is dating for the reason of marrying Yosuke. When Yosuke introduced me to my father and went home, he was there with Papa Katsu's old partner. Sumire, who was suggested by her father to live with the three of them, accepted it because she was worried that her father's activities would be disturbed if she was in a bad mood. One day when they started living together, Yosuke suddenly had work and his father, who was alone with Sumire, pushed him down with an aphrodisiac in his drink.