What if, upon returning to the real world, the hero receives a marriage proposal from the Demon King!? Meguru Kitaki, who was transported to another world and became a hero, clashed fiercely with the Demon King in the final battle—seemingly settling everything once and for all. But when he awoke, he found himself in a hospital in the real world. Reeling from the shock of leaving behind a smooth and triumphant life in another world, Meguru resumes life as an ordinary high school student. After being discharged from the hospital, he encounters a girl who looks like an elementary school student, yet boldly claims to be the Demon King—and even goes so far as to propose marriage! A riotous, rival-turned-romantic comedy unfolds between a daring, naive, and cute Demon King and a returning hero caught in a whirlwind of chaos.