Stepmother Miki, who ran away from home, suddenly visits, surprising her daughter Hiromi and her husband Seigo. That night, Seigo and Miki are enjoying a drink alone, but... When Miki gets drunk, he becomes a kiss maniac, and forgets that he is Seigo's daughter's husband, and cannot help but bite Seigo's lips. Then, perhaps because he has been feeling pent up from not having sex for a while, he forcefully pushes Miki down and straddles Miki wild. The next morning, Miki seems to have no recollection and behaves normally, but Seigo, who is still excited from the night before, as soon as they are alone...