Atsushi is enjoying his single life while his pregnant wife is back at her parents' house. Suddenly, his wife's sister Kiriko shows up without any notice. 'I thought you might be having trouble on your own, so I came to check,' she says. Atsushi assures her he's fine, but Kiriko ignores him and insists on staying over. That night, as Atsushi is taking a bath, Kiriko appears in the bathroom naked…
