Alto Goldfilled, a diligent student at the Ortigia Academy of Magic, aspires to become a powerful sorcerer. But he is unable to become one as, despite his excellent grades and strong commitment to his studies, he fails his summoning class. With the threat of repeating a year hanging over his head, Alto tries following an old, worn-out grimoire in a desperate attempt to resolve his situation. To his surprise, he succeeds and summons a powerful demon named Vermeil. As a sign of gratitude for releasing her, Vermeil agrees to become Alto's familiar, sealing their relationship with a deep kiss. Little does Alto know what else he is capable of and what Vermeil's past hides.

On Halloween night, a young chimney sweep named Lubicchi befriends a man magically conjured out of garbage. Giving him the name Poupelle, Lubicchi is able to recreate a bond he lost when his father died to the tyranny of the Inquisitors—an oppressive force that aims to suppress outside knowledge and the town's true history. But their newfound relationship soon captures a lot of attention, and the threat of the Inquisitors and even the criticism of a few townspeople will test the duo's friendship. In spite of this, Poupelle has struck a particular chord with Lubicchi, and the two conspire to bring the truth to the surface and clear the chimney smoke that clouds the town's skies.