あくまでも、妹が欲しいんです。

I, Shinya Ninomiya, love sisterly tropes but have no real sisters of my own. As I was sketching out my ideal sister with these feelings in my heart, the demon Ririn came to me through the window. She says she can grant me three wishes. Hearing this, I said, "I want a younger sister. Oh, and another. I want more than one." I even provided a detailed list of traits as a part my wish. When I woke up the next morning, my wishes came true and I had two sisters in my house...? A slapstick devilish little-sister comedy! (Source: Ichijinsha Bunko, translated)