Yui Misaki brings a tea to her boyfriend and they talk about a future trip when Maki Koizumi, Yui’s sister, comes in. While talking about having this trip all the three of them, they some jokes about boobs are made. When the night comes, Yui’s man is in the mood for sex, but Yui refuses him because she is tired. He goes to the other room where he finds Maki doing her stretching exercises.