Tatsuya sees off his wife, who is about to give birth, and works hard at the housework. He feels lonely and alone with no one to talk to, when his wife's sister, Maina, comes to check on him. Tatsuya is happy to have someone to talk to after a long time and welcomes Maina, but Maina's real purpose is her body. Maina suddenly bursts into the bathroom. With no way to escape, Tatsuya has no way to resist her super soft, fair breasts.