Y.U.K.I.N.A

At first glance, Yukina Yuzuhara is just an innocent high school girl. However, she has a secret passion: drawing doujinshi. In an unfortunate turn of events, however, her works are found lying on her desk by her teacher. Threatened with expulsion, Yukina pleads for him to overlook this incident, but her teacher's response is unexpected.
As it turns out, he likes Yukina's drawings, complimenting her skills and even offering her advice. Even so, he claims that Yukina's manga lacks a sense of realism and tells her that she needs more practical experience. Of course, practical experience can be had in many ways, but her teacher is fixated on one method in particular...

(Source: MAL Rewrite)