Mitsu is a second-year college student obsessed with sex, even though she's still a virgin. Curious to explore herself, she buys an adult toy, but just as she's about to use it, her childhood best friend, her perfect prince, Hayase, catches her in the act! Just when she thinks her life is over, he tells her to show him how she's going to use it?! As she begins, Hayase's own secret is exposed. They were only supposed to be childhood friends... but from that day on, their special, erotic training began!