The Misfit of Demon King Academy, Vol. 4, Act 2 (light novel)

The truth is out--the fraudulent Demon King, Avos Dilhevia, is a great spirit. And with his legendary power, he seizes control of Dilhade. In order to learn the secret of the great spirit's birth and stop Avos once and for all, Anos must go back in time to Aharthern two thousand years ago. There, he witnesses a loving family torn apart by a tragedy that will explain everything... Every injustice, every tragedy will fall before the Demon King of Tyranny! The misfit's path to domination continues as the Great Spirit Arc reaches its emotional climax!