One day in Staccato, trouble ensues as demons appear and wreak havoc on the townspeople, causing the entire country to suffer. The root of this chaos is the weakening of the "barrier" that has prevented demons from crossing over into the human world. The person responsible for upholding the barrier, Queen Horn of Sforzando, has been losing her strength after many years of doing so. The Hell King Bass is attempting to break through the barrier to release their "supreme leader", Kestra (Orchestra), who possesses unparalleled power but is currently trapped in the human world.