It is incest to the younger sister who is so disliked. It was made by the aphrodisiac and melomezzo

I came to live with mikako in my parents' remarriage. I want to live with the opposite sex, and it is colored though mikako's underwear is colored. Mikako who dislikes Yoyogi physically dislikes and rejects it. Yokiku who cannot give up mikako still makes mikako mono by using the bought aphrodisiac. I feel like my body is disgusting...