The universe is not just one. Within the overlapping layers of the multiverse, there exists another Earth that looks exactly like Earth. In "MultiEarth ?0073", which has entered an era of cosmic coexistence, crimes involving the exploitation of energy-based lifeforms known as "Emorgy" are breaking out one after another. Reiji Doki, an investigator for the Galaxy Federal Police, is Gavan Infinity, the only person in the universe permitted to claim the title of "Space Sheriff Gavan". However, he is stationed in the backwater Archives Department. His true objective is to investigate Emorgy crimes across dimensions. Chasing these inter-dimensional threats, Reiji leaps through space-time, encountering the Gavans of various dimensions and joining forces to bring justice to the multiverse. "Jo-Chaku!" The Space Sheriffs Gavan transcend the boundaries of the universe to strike down evil!
In this two episode straight to DVD sequel to Kamen Rider Drive, Gou Shijima AKA Kamen Rider Mach helps an old friend from the series who is now in trouble with the law while at the same time Genpachiro Otta comes to terms with now being middle aged as he teaches a newly revived Heart how to be a Kamen Rider.
Not long after the events of Kamen Rider Gaim, Kouta and Mai, who are now ruling over a new planetoid as gods, are attacked by Megahex, a cybernetic being with ambitions of making the whole universe one with it's self in a symbiotic manner. Mai is taken prisoner by Megahex who then chases Kouta back to earth where he briefly fights Megahex to try and save Mai with the help of his old friends from Zawame City, but after struggling to hold their own against Megahex's army which is commanded by restricted versions of some of their old enemies. Meanwhile in another part of the Japan, Shinnosuke and the rest of the Special Investigation Unit are dealing with Phantom Thief Ultimate Lupin, a mysterious criminal who is running wild in the city. Moments after the case is solved, Megahex's invasion of earth expands to the rest of Japan and after a moment of confusion, Shinnosuke and Kouta team up to stop Megahex and save Mai along with the rest of the planet



