My older sister is a villainous lady. In order to make my beloved older sister look at me, I, a villainous young man, broke the engagement between the crown prince and her—but what was that method? ~Older sister, I'm sorry, but I just have to make you my bride~

My beloved older sister became the Crown Princess, it seems. But I really hated that guy, the Crown Prince. So I decided to separate him and my sister... This is a story about a Duke's daughter older sister who doesn't know the true face of her devilish younger brother, and Fluery, the innocent(?) ten-year-old younger brother of a villain's son who loves scheming. Note ※There is no blood relation. The younger brother is a step-sibling (adopted child). Bedwetting.