Confiscating Girl Koume

As a 35-year old high school teacher, he finds himself with zero friends. He tries to make friends with the other teachers, but they treat him like trash. He doesn't know what to do, until Koume, the most popular girl in class, offers him a helping hand. But she doesn't want to be his friend, she says, “I'll be your teacher." What does she mean by that?

(Source: Comic Days, translated)