This anime is about Satan, who is the Mighty Devil King and is just about to conquer Enta Isla but Hero Emilia and the rest of humanity, united and defeat Satan. But just before defeat The Devil King and his strategic advisorAlciel retreat through a magical Gate.
In addition, they wind up in Tokyo where, magic does not really exist. Which means, the Mighty Devil King and his Advisor are in Human form?And are forced to live life as ordinary human. Satan get's a Part Time job at the Local MgRonald's and Alciel stay's at home and research on how they can get back home.
But there is one thing they did not count on and that was Emilia following them through the Gate. This leads to a great comedy.
I loved it and could watch it over and over again.