友達の家で妹果林と二人っきりになってしまうさとる。果林の提案で「負けた方が何でも言うことを聞く」という罰ゲームを行い、さとるは負けてしまう。果林は「私専用の椅子になれ」と迫る。さとるは言われるがままに椅子になると勃起に気づき果林はそれを鑑賞して罵っていく。翌日もまた果林に迫られて今度はセックスしてしまう。びゅるびゅると搾精され、奴●に落ちていく。
Satoru finds himself alone with his younger sister, Karin, at a friend's house. Karin suggests a game where the loser has to do whatever the loser says, and Satoru loses. Karin demands that he become her personal chair. Satoru does as he's told and becomes a chair, and Karin notices his erection, admiring it and berating him. The next day, Karin demands sex from him again, and this time they have sex. He is milked dry and falls into slavery.

– JavGG.net