The Strongest Magician in the Demon Lord's Army was a Human

Right now, the humans are engaged in a fierce battle with the Demon Lord Army, among which the most striking member is the commanding magician of the Immortal Brigade, Ike. Although celebrated as the trusted aide of the Demon Lord Army, Ike hides a secret from surrounding demons, that is, he is actually a human, a mere mortal reincarnated from Japan!