With memories of his father's inexplicable death still haunting him, Daichi follows a mysterious rainbow to his childhood home Tanegashima Island to investigate. As Daichi delves deeper into the mystery of his father’s death, a strange encounter with an unusual girl plunges him into the middle of a battle! Now, Daichi must become the pilot of the Earth Engine— a giant robot that only one known as a “captain” can pilot— is he wants to protect the world.