In Earth's parallel world, Polyphonica, spirits and humans live together. Spirits survive on the music played by "Dantis", humans who have the ability to play special music that summon the spirits. Dantis are highly respected in Polyphonica, and the higher the skills of a Dantist, the more powerful and obedient spirit can be summoned to serve the Dantist.
 
One day, a female spirit, Corticarte hears a song being sung by a young orphan named Phoron. She appears before Phoron and makes him a deal: the next time Phoron sings the song; she'll appear and protect him from all manner of evil beasts and wickedness to come. Years later, Phoron attends Commandia Academy, a prestigious music school for Dantists, but he is a mediocre Dantist who has not been successful summoning spirits. Feeling melancholy, he offhandedly sings the song that called Corticarte years before, but his unconfident singing voice summons a bad-tempered, insanely jealous Corticarte that causes all kinds of problems around him at school!