Akademii no Kenjutsu Shinan ni Natta

The protagonist is reincarnated as a mob character from a popular novel, Kageyama Ayumu. In order to leave the task of saving the world to the original protagonists and enjoy a rich and comfortable life, Ayumu decides not to interfere with the flow of the novel. However, he learns that there is discrimination against those who did not graduate from hunter schools at the academy where he works. In order to avoid being looked down upon by his fellow teachers and to live a comfortable life, Ayumu decides to change the content of the original a little to become strong enough to at least protect himself, and so begins his reincarnated life.

(Source: KENAZ, translated)