Several years into our marriage, my mother-in-law suddenly comes to Tokyo and asks to stay with us for a week after being scouted as a lingerie model. My wife strongly objects but reluctantly lets her stay until the excitement wears off. That night, I peek into a lit room and find her posing in lingerie, still unwilling to give up her dream. I cannot take my eyes off a side of her I have never seen before. The next day, she reveals that she noticed me watching and asks me for a private favor, beginning a week in which we repeatedly surrender to temptation.