Aya Hoshino

Aya is one of the top students in Ran's class, but she was secretly doing enjo kōsai to earn money (only announced in the first chapter and episode), since her parents were very strict about her being in number one in academics and wouldn't let her do any part-time jobs or go out. Ran found out and confronted her about it, making her realize that she was doing the wrong thing fortunately before Aya "did it" with somebody.