Sakurako washed my underwears without hesitating. Azusa swore at me when she got drunk. I liked Tsubasa's cheerful voice. Until the day we were informed that we weren't related by blood. Nothing was changed but it was true. I was so shocked to hear that, and immersed in inventing a drug to forget it. Finally, I invented a liquid drug called "No.21". Once I drink it, I become invisible. I immediately drink it and go outside, and rape the girls at random including a female high school student, my ex-homeroom teacher and so on. I come back to my house later on, and start a new life with sisters again. Yes, a new life....