Kaizaki Najimi is a 17-year-old genius high school boy who is satisfied with his everyday life. He goes to school, talks with his friends, eats lunch together with them, and goes home when the last chime of the day rings. One day, an underclassman asks for his help to pretend to be her boyfriend for a day due to a certain circumstance. He deicides to help her, thinking what could possibly go wrong.

This story revolves around Kaizaki Najimi and his friends, as well as his crush in his everyday life. What comes after helping his underclassman?