The battle finally begins! Friend or foe? The strongest new Rider appears.

Shouichi encounters a teenage girl called Sayaka, who ran away from a military facility because of an attack by the Ant Lords. Sayaka has a supernatural ability to foresee the future. Risa Fukami, of the military group GA, wants to use that power to enhance the newly-made G4 System, which was based upon designs stolen from Ozawa. Now, Agito and Gills must fight to stop the Ant Lords' attack, as G3 and G4 settle their score.