After his wife left for a trip, Hiroshi was enjoying a rare taste of living alone. That's when Haruna, his wife's older sister, came over to visit. As Haruna drew closer and flaunted her alluring figure, Hiroshi's heart began to race. When he tried to take a bath, Haruna forcefully barged in, saying, "Let me wash your back for you." With her full breasts pressed against his back, their relationship took a passionate turn.