私は義理の妹のお尻をファックし、それと引き換えに彼女を新しい彼氏と付き合わせます。

My stepsister asks me for permission to let her go see her boyfriend, I am jealous of her because she is the only one who can have sex with me, therefore I tell her that I let her out in exchange for making me cum in her ass, which she agrees and earns permission.