During a record-breaking hot summer break, Ryosuke tells his aunt Kotoha that he's got his first girlfriend. But Kotoha lost her husband and has been suffocating on her own loneliness, and his awkward innocence takes her self-control away. Slipping past the rest of the family, she seduces him gently under the banner of practice — and the pretence of instruction peels away, turning into something feral. On the last day, Kotoha ties his wrists and ankles down and loses herself in orgasm control, wringing every drop out of his stamina. Seven days of guilt, with no way at all to resist his aunt.