A demon king reduced to working the graveshift at a fast-food restaurant is the entire joke, and it never stops being funny because the show treats it like a tragedy. Sadao is genuinely trying to climb the corporate ladder at MgRonald's with the same ruthless ambition he brought to conquering worlds. The romance sneaks up on you because watching him fall for the hero he was supposed to destroy matters more than either of them conquering anything.

Demon Lord Satan is close to conquering the land of Ente Isla with his demon armies when the hero Emilia defeats him, and he escapes through a dimensional portal into modern-day Tokyo. Without magic in this world, he and his loyal general Alsiel are stuck, broke, and struggling to cover the rent. His solution: take the name Sadao Maou and start working at MgRonald's, a local fast-food restaurant. His talent for conquest is no help behind the counter, but he still means to return home someday, and in the meantime he sets his sights on rising through the company and ruling Earth one happy customer at a time. What emerges is a comedy about a hapless demon lord facing part-time shifts, household chores, and the ordinary grind of daily life.