Makoto ends up alone with his younger sister Yuna at a friend's house. At Yuna's suggestion, they play a punishment game in which the loser has to listen to whatever they have to say, and Makoto loses. Yuna urges him to use his own chair. Makoto does as he is told and turns into a chair, and Yuna notices his erection, which Yuna admires and curses at him. The next day, Yuna presses him again and this time they end up having sex. The sperm is squeezed out and falls into the slave.
