To make my sister, who mocked me for being a virgin, understand by using her incredible penis. (Tenma Yui, Kikuchi Haru, T-38005)

Although they've grown up, they're only interested in 2D, have no girlfriend experience, and have a virgin brother. The older sister, Yui, and the younger sister, Haru, play pranks on and seduce their brother while playing with his genitals... However, their brother is actually a virgin penis with the ability to ejaculate continuously!