"Isn't sex for making babies? Then just do it when you need a baby." Kinu is a high school girl known to be sharp-minded and a little too serious. She rejects her boyfriend's advances and spends all her time studying. One day, she encounters Haruka Mihara, the most handsome guy in school, making out with a girl in the reference room. Witnessing the scene leaves her all shaken up and unable to stand. The next day, she calls for Mihara in private and offers him a proposal... A game between a serious high school girl and a charming popular guy begins!