Saitei Chingin Maou: Rekidai Saikyou no Maougun, Sono Ashi o Hipparu no ga Oshigoto desu

Aquas is a man who lives only for his hobbies and training. He was content with his modest life as the lowest-class, bronze-rank adventurer. One day, however, the goddess of creation, Uiras, suddenly appeared in his home and offered him a job—to become the Demon King and stand in the way of the strongest demon king's army in history. His only compensation would be the minimum wage, but even so, Aquas accepted the job.