The day before summer vacation starts, Daichi who is a high school boy, sees a rainbow on TV in an island. “I’ve seen this rainbow before…” He is suddenly urged to visit this island to find about this rainbow, bits of forgotten memories from the past and his father’s mysterious death. At the island, he encounters a gigantic unknown robot called “Earth Engine”. He is asked by a crew member, “Are you the Captain”? From then on, Daichi is sucked into the space battle against robots from Uranus, “Kiltgung”. When the stars shines brightly in the sky, the battles begin.