Musashi Haruno, now a middle school student, continues to pursue his great dream of becoming an astronaut, a promise he once made with Cosmos. However, after news breaks of a rocket accident leading to the suspension of space development, Musashi nearly falls into despair. At that moment, a mysterious girl named Shau appears before him. She guides Musashi into a strange otherworldly space and shows him a vision of his own future, ten years from now. What he sees is a looming crisis: the destruction of Earth itself, brought about by Sandross, the most fearsome destroyer in the universe!