Sei Chishiki no Nai Imouto ni, Ecchi na Massage o Shitemita Kekka...

I have a younger sister. Her name is Kurumi... Her body may have grown and developed nicely but... Inside her head, she's still just a little girl. In other words, me and Kurumi are alone together. On a day, with no interruptions, under the guise of a "massage", I teach her body the forbidden fruits of pleasure... The choice of whether Kurumi ends up with a fortunate... or misfortune future, is entirely at your fingertips...