High school student Natsume Harumi has a crush on his biology teacher Koba. In order to spend more time alone with Koba, Harumi purposely failed his biology tests so he could attend Koba's supplementary class. However, one day, a student named Nei attended the class. On the first day, Nei slept through the whole class, so he asked Harumi to teach him. Harumi reluctantly agreed. "If you understand everything, then why do you need to take the supplementary class?" Just one sentence from Nei, and Harumi can't hide his anxiety. (Source: Home-sha, translated)