Riding the train far away from Tokyo, the younger brother-in-law returns home to his family residence for the first time in a while. Reunited with his sister-in-law, Kaori Otonashi, he becomes captivated by her stunning appearance and refined, mature body. As they spend each day together, feelings slowly begin to stir within him. Then, in the moment when her husband steps out and the two are left alone, a new relationship sparks between the brother-in-law and the married woman.