Youki dies in a traffic accident and is reborn in a fantasy world, not as a legendary hero but as a mid-ranking demon with far more power than his post suggests. With no ambition to rule, he idles as a low-level guardian in the Demon King's castle until the hero's party storms in and he knocks them all out on a whim. While healing them up to send them back to town, he lays eyes on their priestess, Cecilia, and falls for her at first sight, vowing to confess his feelings even if it means betraying the Demon King.