Sasagawa and his wife Miyako live in a regional city near the Kanto region. Their son attends a university in Tokyo, so they live alone at home. One day, Miyako's younger sister Sakiko comes to visit for the first time in several years. Miyako is about to have a hernia operation, so she has come to look after her. Sasagawa swallows his saliva when he sees Sakiko's body for the first time in a long time. After his wife goes to the hospital, Sasagawa borrows a hidden camera from an acquaintance and sets it up in the house, and begins to spy on Sakiko...