Kasugai-kun wa, Mousou JK to XX shitai

High school girl Mikami Kiri is considered by those around her to be a neat and tidy highbrow. But the truth is that she is just a normal (?) JK who loves naive boys and fantasises about them every day. One day, she meets a boy who is not so nice to her. One day, Kiri is confessed to by Kasugai, a playboy who is the complete opposite of a naive boy. Kiri is interested in Kasugai's story of his first experience, and in return for listening to his story, he kisses her. From that day onwards, their impure relationship begins as they recreate Kiri's fantasies - or does it?