I live alone in Tokyo in a tiny apartment and suddenly I've started living with my younger sister (Mei). Before I knew it, Mei's big boobs had grown so big that she was defenseless at home and always letting them slip out, so I had a hard time knowing where to look! I couldn't resist and forced myself on her and came inside her... But that night, Mei asked me for creampie sex, saying, "I've been horny for a long time too..." We've entered into a secret relationship that I can never tell my parents about...