Leo, the strongest hero who has no place to go anywhere after saving the world. Power that is too strong can not enter the peaceful world. A place of employment where he arrived – the former enemy, the Magus army!

Source: MU

After saving the world, the strongest hero Leo became someone who is not wanted in the peaceful human world. He was too strong. Exiled, he seeks a job at the Demon King's Army, which he had defeated and needs to be rebuilt. The Army had many problems: too much work, financial troubles, etc. Leo starts to make things better using his power. Leo encounters Echidna again, and asks her why she invaded the human world.

Source: KADOKAWA