Impregnated And Ravaged Your Sister Because I Hate You And It Makes Me Feel better. Moko Sakura

大嫌いなアンタの大切な妹を憂さ晴らし種付けレ×プしました

The protagonist has an asshole boss who forces him to work overtime way too much and makes his life so miserable. The result ends up being her wife dumping him. This made him rage badly, and he ends up setting his attention on the younger sister of his boss for proper revenge.