Aokana Four Rhythms Across the Blue — in a world where flying through the sky is as easy as cycling, the Flying Circus sport is the most fashionable. After the discovery of anti-gravity, special shoes that allow a person to fly, Anti-Graviton Shoes, conquered the world by storm. And with Grav Shoes, completely new technologies came for people to explore. Soon after, this revolution in technology spawned a new sport, the Flying Circus, which used shoes to compete in open skies. Masaya Hinata, who was once considered a child prodigy, turned away from the Flying Circus, having suffered a crushing defeat, although there was another reason.