Six years after the Wind Revolution cost him his kingdom, Kal-el Albus boards the flying island Isla to enroll in its aviation course, carrying no plan beyond revenge on Nina Viento, the revolution's living banner and now the island's administrator. As Isla sails toward the edge of the sky, he keeps running into Claire Cruz, a sheltered girl his own age who barely knows how to talk to anyone, and the two grow close over the long voyage. This is the original light novel behind both the manga and the TV anime.