While his wife was pregnant and visiting her parents' home, Kazuya struggled with the unfamiliar housework. However, his efforts were in vain and the house was getting messier. At that time, his wife's older sister, Yuri, showed up to help with the housework. Kazuya was confused by her sudden visit but happy. However, Yuri's real purpose was to release her pent-up sexual frustration with his sister's husband. Unaware of this, Kazuya was relieved to have been given all the care he could ask for and went into the bath. Then Yuri came in with a bewitching smile on her face and washed his back...