Shunpei accidentally catches his brother-in-law Junpei taking a shower. Seeing this, Chizuru grows concerned, wondering if he's troubled about his relationship with his older brother. However, Chizuru becomes entangled in a passionate affair with her husband's younger brother, writhing in emotional turmoil as her enormous breasts shake wildly during intense creampie sex. That fleeting moment becomes the catalyst that deepens their forbidden bond.