A stepmother named Yuuko Shiraki visiting his in-laws. Arriving there, Yuuko meet her step-son named Manabu. Manabu do not like the presence Yuuko as surrogate mothers.

At night, Manabu woke up and wanted to pee. He walked through the rooms of their parents. Inadvertently, Manabu see their parents having sex, and Yuuko know Manabu presence. But let Manabu see Yuuko.

Until finally, Manabu and Yuuko have sex and his father didn’t know it until Yuuko back to home.