A sister-in-law who comes to a sexless couple one day. She is a neat and clean wife who is pointed out that she cannot have children. She will receive infertility treatment as her sister-in-law says and her treatment full of shame begins. Stimulated by her first sexual feeling, her obscene training act draws out Riko's carnal instinct. At some point, Riko transforms into a prisoner of sex and she dies.
