While Kenji's wife is away staying with her family for childbirth, his sister-in-law Yuuna visits to check on him. Struggling with unfamiliar housework, he welcomes her help, unaware that her real target is his body. Every time she cleans, she teases him with glimpses of her cleavage, glowing tan skin, and long shapely legs until he cannot hide his erection. As he scrambles to cover it up, she whispers, “She's not here, so it's fine. She'll never find out...”