[Machine Translation] Second semester. Sakita was buoyed by his first meeting with Mai in a long time, but what awaited him was a cruel question, "Who are you? was what awaited Sakita. It seems that due to puberty syndrome, Mai has been replaced by someone else. That someone was Nodoka Toyohama, a new idol with blonde hair and gal makeup. She is Mai's half-sister who ran away from home after a fight with her mother. The two pretend to live with each other, but Nodoka seems to have something she wants to say to Mai. If they don't solve the problem, Mai and Nodoka will have to put off their flirting again! This is the fourth installment of our fushigi-style adolescent romantic comedy, "Don't look at my sister's body with pornographic eyes! The fourth installment!