Rio's brother-in-law, Yuta, comes to stay with her temporarily while he searches for a job. At first, Rio warmly welcomes him, but Yuta harbors dark, hidden desires. Secretly obsessed with her, he begins sneaking into her room to steal glimpses of her underwear and spying on her intimate moments with her husband. Though Rio gradually becomes aware of his lewd gaze, she pretends to ignore it. But Yuta, consumed by lust, can no longer restrain himself and violently takes her. Subjected to rough, animalistic sex far beyond anything her husband has ever given her, Rio repeatedly reaches climax after climax. These intense pleasures slowly take control of her mind, eventually carving a deep, inescapable mark upon her body.