One night, just before summer vacation, Manatsu Daichi, a second-year high school student, spots a strange circular rainbow hovering in the sky above Tanegashima and heads there alone. He has seen this rainbow before. Carrying memories of his father's mysterious death and an encounter with a strange boy and girl, Daiji arrives on the island as the alarm of a building labeled Earth Engine sounds. Someone asks him if he is a captain, just as robotic intruders from Uranus called Kill-T-Gang arrive. The battle around the shining stars is about to begin.