Sekai de Tada Hitori no Mamonotsukai: Tenshoku shitara Maou ni Machigawaremashita I'm the Only Monster Tamer in the World and Was Mistaken for the Demon Lord

Synopsis

After searching for a long time, Noah finally found the "Job Change Tome." With it, he just might be able to get away from his current job of "Hero" and its responsibility! Or so he thought. Because the new job that had been granted to him, "Monster Tamer," was one he'd never heard of...!? (Source: Kadokawa, translated)