It's a bird! It's a rocket sled! It's. . . a convertible girl?! When Hoichi's grandfather calls him in to pilot the giant robot Exaxxion, Earth's one tool to stop a violent alien invasion, the gutsy high school kid soon finds himself fighting off a nasty pair of forces. It's not as if the Riofaldian alien robot army wasn't enough, now the teen has to fight against the UN military as well! As he rushes to his grandfather's secret base, Hoichi discovers that there's more to his assistant, Isaka, than meets the eye. Way more!