Tatsuya is doing housework to see off his wife who is about to give birth. Just when I was feeling lonely with no one to talk to, my wife's sister Maina came to check on me. Tatsuya, happy to have someone to talk to after a long time, welcomes Maina, but Maina's true purpose is her body. Maina suddenly bursts into the bath. With no way to escape, Tatsuya is forced into the clutches of her bouncy white breasts, and there is no way to resist him...