On January 1, 1995, a G-Reactive fighter plane was being tested, while it was hit by a mysterious rainbow light and disappeared. 5 years later, two boys, Billy Kimura and Penny Carter, meet at a train station where a new bullet train utilizing G-Reactive was being launched. However, to their shock, the train was hit by a rainbow beam of light, and disappeared. After a series of events and acquaintances, the two boys discover that aliens were beginning to invade Earth. Fortunately, scientists developed the Sky Knight, a fighter plane capable of defending the world. As the extraterrestrials begin to invade, Billy, Penny, and their comrades begin their attempt to save the human race from the alien menace.