The once‑infamous Demon King Satan of Ente Isla, forced to escape Earth after his defeat by the heroine Emilia Justinia, now resides in Tokyo under the civilian name Sadao Maou. He has become an exemplary worker at a nearby fast‑food chain, supporting his former lieutenants Alciel and Lucifer who accompany him in Japan while steering clear of clashes with Emi Yusa—the alias for Emilia—and the angelic observers who keep tabs on him.
During a heated quarrel between Sadao and Emi, a tear in reality opens, delivering an enigmatic apple that conceals a young child named Alas Ramus. To everyone"s astonishment, the infant declares Sadao and Emi her parents! Though hesitant, Emi consents to aid Sadao in raising Alas Ramus, but their fragile routine is shattered when the archangel Gabriel arrives with dire tidings. He insists that both Alas Ramus and Emi"s holy blade must be taken away—otherwise the world will crumble.
Rejecting Gabriel"s bleak forecast, the former Demon King and the heroine must set aside their past enmity and collaborate to safeguard what matters most to them.
