Shingo spends his weekends at his girlfriend Miu’s home, but their routine changes when her older sister Yuki moves in after her husband’s affair. Yuki works as a personal trainer, and Miu practically forces Shingo to let her train him. With Yuki’s muscular body and beautiful face pressed so close, he gets rock hard. She notices his erection and makes each workout more seductive until the hands-on training ends in sweat-soaked cheating sex and a creampie.