Manatsu Daichi, a high school student, notices a familiar round rainbow in the sky above Tanegashima before summer vacation. The island holds memories for him, including the mysterious circumstances surrounding his father's death and encounters with a boy and girl he met earlier. The Earth Engine building on the island is ablaze, and as Daiji arrives, he's asked if he's a captain just as Kill-T-Gang, robotic intruders from Uranus, appear. The stage is set for a battle involving the stars and the robotic forces.