Bikei Shisho-san wa Zetsurin Nikutai-ha Nurunuru na no wa Mukimuki no Sei de Dekiai Saremashita!?

Histoire

The handsome, muscular librarian with messy hair and thick glasses was my favorite reader! Mirabelle, who works at a cafe, actually has another side to her: an erotic novelist. In order to replenish the erotic passion she loved in her previous life, she made her debut as an author by writing her own novels. Her secret pleasure at the library where she always writes is observing the muscular librarian with his messy hair, thick glasses, and tattered shirt. She's so obsessed with his sexuality that she was trying to write a new novel with a character modeled after him.

Synopsis via AniList (en anglais).