Twenty years after being defeated by a hero, the Demon King has reincarnated as an ordinary young man named Mao and is living a peaceful life in the modern world. His quiet routine is shattered one day when a small child wearing a pot on his head and carrying a sword shows up at his door. The child is the reincarnated hero, Yuu, and the sword he wields is the same one that once defeated Mao. From that moment, Mao finds himself thrust into the role of an unexpected guardian.

The story follows Mao’s reluctant but gradually devoted efforts to raise the child hero, who has no memory of his past life. Their daily life becomes a series of comedic and heartfelt parenting challenges: nursing Yuu when he is sick, navigating playdates with other parents, training sessions orchestrated by Mao’s former demon army lieutenants, and even dealing with the meta-humor of a manga editor trying to spice up the narrative. The setting is a recognizable contemporary world where reincarnated beings from a fantasy realm must blend in, leading to absurd situations where demon lords chat about school lunches and four heavenly kings become overbearing babysitters.

Supporting characters include Ogurisan, the reincarnated “Strength” heavenly king of the former demon army, and Yamino-san, the “Knowledge” heavenly king, both of whom assist in the unwieldy task of child-rearing. As the story progresses, Mitake Rin, the reincarnated “Skill” heavenly king, also appears. The underlying narrative arc moves from mere caretaking toward the question of whether Mao and Yuu can truly become a real family. The series builds to a conclusion that explores what it means to love and protect someone beyond past enmities, ending with a heartwarming resolution that answers whether a former demon king and a former hero can forge a lasting bond.