When aspiring pop star Hatsune Miku saves an odd man named Kaito, she and her fellow "Vocaloids" band mates Rin, Len, and Luka are drawn into danger as winged people attack their home in modern-day Japan. Kaito, a song mage who lost his wings, and his friend Gakupo, a warrior tainted by dark magic, aid Miku and her friends as they try to stop the end of the world. Now complete.

In a small village, Miku Hatsune grew up scared of "Demon Prince" tales. But the Demon Prince is real – Prince Kaito, a man cursed with a monster's form for breaking the fairy Luka's heart. When fate leads to Miku spending all winter at his castle, he and his ghostly knight Gakupo think they might have a chance to end the curse for good! But can shallow Miku come to love a beast?