Kore Kiri Nante, Dare ga Itta?

I don't know why... I, Mion Nakamura, am getting mad at a handsome guy in front of me who is about to take off his lower body;; Hirakawa, the class president with excellent grades and the highest school caste, is trying to have sex with a girl. However, Mion runs into him and is forced to play the game as punishment for ruining the friendly atmosphere! In order to have a peaceful student life, she cannot go against the upper caste members of her class. ...What is the content of the game proposed to Hirakawa?