A brief description of the How the Demon Emperor became a Butler manga:
It was always like this: the demon emperor had the highest title, which could only be passed on by inheritance. Leaving this world through the betrayal of a friend, he was reborn. Except that he lost his powers. His faithful companion became his inner demon, which dragged him into dubious affairs, if not troubles at all. In the end, he became withdrawn and closed. The new position was also embarrassing. He became a butler in a noble house, the daughter of a nobleman. How will they behave when they’re around, Mistress and the inner demon? How will he live on his way from the demon lord to the butler. How will he be at the head of a clan that is dying? And how will he get back to the top of the world.