Nano Saikawa is a great teacher, beloved by colleagues and students alike. But lately, her after-hours activities could get her into a lot of trouble: she is in a relationship with one of her students, Souji Kuga.

This strange situation began when Nano decided to go to a marriage interview at the behest of her father's friend. She and her partner, Souichirou Takamiya, hit it off, but she can't shake the feeling that she knows him from somewhere. After a successful date, Souichirou proposes, and they fall into bed together. But after he calls her "Miss Saikawa" during sex, she realizes that the man in front of her is actually Souji, who admits that he switched places with his brother Souichirou because he wanted to be with her.

Since Souji is still in school, their families agree that it would be best if Nano and Souji got married after Souji graduates, but Nano isn't sure she wants to be in a relationship with him. However, she can't deny how he makes her feel, and his touch always leaves her wanting more.