The university photography club's member, Natsuki, is known for helping many men lose their virginity. However, Hirata, a freshman, has his eye on Fuyuki, who is Natsuki's older sister and works at a bookstore. She is 30 years old and has never had a boyfriend before. Despite looking younger than her little sister, she is a late bloomer when it comes to relationships. Can you help Hirata in winning over this shy and introverted woman by introducing him to the joys of sex?