Hiroshi visits his girlfriend's family home in the countryside to congratulate her on her marriage registration. Her mother greets him and tells him that she is his stepmother, a young, beautiful and intelligent woman who is apparently his stepmother, as she is his father's second wife. Hiroshi is kindly allowed to stay at her family home that night, but after witnessing his beautiful mother's naked body after a bath, he becomes aroused and cannot fall asleep. When he has no choice but to leave the room, he catches a glimpse of his mother's bedroom...!