MUDR-107 Erika Arimura spends three days having sex in her older brother's room before her younger sister, a sexual monster who is going to boarding school in the spring, moves out.

On the day my parents are away from home for a memorial service, I'm alone with my sister who is about to move in for the first time in a while... - When he sees the defenseless appearance of his little sister, who the family is proud of because she's good at studying and is cute, he can't resist his desire and forcibly rapes her. - Then, my sister told me that I might actually have a stronger sexual desire than other people. - From then on, I had sex with my sister over and over again until the day I left home to move... This is a record of that day.