So there is this evil Overlord Satan, King of Demons – a character who has been getting lots of anime screen time recently. And the armies of the world of Ente Isla assemble their bravest heroes, to fight the demon hordes and end the tyranny of evil. There is a great showdown and the heroes clash with the Demon King and First General, and a rift in space and time opens, through which the two are teleported to another world.
From there on, things go awry. They’ve ended up in modern day Tokyo, a decidedly un-magic place, so their magic powers don’t regenerate. The Demon Lord and his First General end up living together as roommates in a tiny, run-down apartment, and the former one starts working part-time at a certain burger joint. Short-term goals involve becoming a shift manager and using the employee bonus program to eventually achieve world domination.