Mitsuru, the younger brother-in-law, harbored secret feelings for his sister-in-law Izumi (42). Izumi, too, had become aware of Mitsuru's lingering male gaze. One night, Mitsuru accidentally witnesses his brother and wife having sex. Noticing his shock, Izumi gradually begins to tease and seduce him. Overwhelmed by the intense feminine scent emanating from his older sister-in-law, Mitsuru realizes his heart can never return to normal. The complex emotions between them continue to deepen.