義理の妹を見ると、彼女が好きなようにセックスしたくなります。

He has a very rich stepsister, and he couldn't resist the urge to look at her in his room because he knows that she likes to pamper herself very well in the afternoons, so he devised a way to be able to see her while she pampered herself and to be able to enjoy all that body, to be able to see her naked touching that delicious vagina she has and little by little he awakened the desire for her to realize that He was there and will end up venting his passion and desire.