THE STRONGEST MAGICIAN IN THE DEMON LORD'S ARMY WAS A HUMAN

Ike is a powerful magician and the leader of the Immortal Brigade, part of the Seventh Corps of the Demon Lord’s Army. He single-handedly conquers fortresses and pushes back the armies of humanity. Neither Dairokuten, the Demon Lord, nor Ike’s loyal soldiers know his darkest secret—he is a human in hiding! But can he keep his secret safe and bring peaceful coexistence to demons and humans? (Source: Crunchyroll) — Description from AniList community (anilist.co).