Detecting a new wave of negative Emorgy, Reiji travels across dimensions to MultiEarth Φ5791. On Φ5791, where trains travel through outer space, humanity has been digitized, and the conductors are robots. Just then, an AI malfunction causes the space railroad to go into a runaway spree. Amid this crisis, Reiji transforms into Gavan Infinity and attempts to stop the runaway train by teaming up with the only Space Sheriff Gavan on MultiEarth Φ5791...!?