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 has conquered nearly everything in his home world when a hero named Emilia suddenly strips away his power and banishes him to modern-day Tokyo. Stripped of his dark magic and supernatural abilities, Satan finds himself broke, powerless, and desperately needing rent money. His solution: get a job at a fast food restaurant. Forced to abandon his villainous ambitions and work minimum wage alongside college students and part-timers, Satan discovers something unexpected. The skills that made him a formidable tyrant, when redirected toward customer service and team management, actually make him a model employee. He's diligent, reliable, and weirdly good at his job. Meanwhile, Emilia tracks him to Tokyo under her own circumstances, and the two former enemies find themselves navigating the same mundane challenges of survival in Japan's demanding job market. What emerges is a comedy about starting over from nothing. Satan's journey from world-ending villain to hardworking fast food crew member becomes a strange meditation on purpose, ambition, and what happens when you're forced to build something new from the ground up.