Reiji Doki, an investigator for the Galaxy Federal Police, is Gavan Infinity—the sole individual in the cosmos authorized to bear the title "Space Sheriff Gavan." Yet he languishes in the marginal Archives Division, enduring daily ridicule from detectives in the First Investigative Division.
Setsuna, known as Gavan Bushido, the Space Sheriff Gavan of MultiEarth Λ8018, confronts Reiji, who has fused with Gavan—a being that shouldn't exist in two forms...
Reiji, pursuing a new Emorgear negative wave, heads to MultiEarth Ι5109. There, he begins investigating an Emorgear incident where humans turn into bubbles, alongside the duo of Kiki Iwai and Kotobuki Takanari from the Galaxy Federal Police's Forensics Division.
On MultiEarth Σ3302, a series of bizarre incidents occur where vital facilities vanish one after another! Reiji, dispatched to the scene, encounters the Galaxy Federal Police investigative duo: Mikuro Arimoto and Shoko Hanemura. Though shocked by Arimoto's seemingly impossible existence, Reiji begins investigating alongside them.
Setsuna and Peacekeeping Corps Chief Rui Amou were racing to arrest the smugglers conducting clandestine deals on MultiEarth Λ8018. Amidst this, Amou was abducted by an unknown assailant. Though every moment counted, Headquarters orders Setsuna to stand by...
While out shopping on MultiEarth I5109, Kiki and Kotobuki encounter Fuware and Emu, a mother and daughter on the run. Just then, the phantom thief Fade, who is pursuing them, appears, and Kotobuki fights fiercely to protect the two.
An incident occurs on MultiEarth A0073. Not only the First Investigation Division, but also Reiji and Colonel Date from the Archives Division rush to the scene. Suddenly, a black Gavan appears, and the colonel is injured. Reiji sees the figure of his former senior, Taito Gato, superimposed on the colonel...!?
A series of mysterious runaway incidents has occurred on MultiEarth ∧8018. The runaways appear to be caused by long-range sniping by a Nega Emorgy. Setsuna, recalling a man who once served as a sniper during an interstellar war long ago, begins an investigation alongside Reiji and AGI, who have rushed across dimensions to join him.
In order to have the words of the previously missing Emorgear Yukaida analyzed, Reiji heads to the Galaxy Federal Police Forensic Division on MultiEarth Ι5109. There, Kiki and Kotobuki are in the middle of a huge fight for some reason. Just then, a new species of Emons that multiplies infinitely appears, putting Earth Ι5109 in danger of destruction!? Even in the midst of this emergency, Kiki and Kotobuki continue to fight, and to their surprise, even the Phantom Thief Fade shows up...
On MultiEarth A0073, Reiji and his team head out to inspect the Cosmo Gavarion’s new enhancement unit. Just as they marvel at the dragon-themed unit, Space Sheriff Gavan Raiya—Kunai Kazanami—suddenly appears, dressed like a ninja, and attacks them. If he came from another dimension, does that mean Kunai is a dimension-hopper like Reiji...!? Reiji transforms into Gavan Infinity and clashes fiercely with Gavan Raiya...!
After escaping from the interrogation room on MultiEarth A0073, Kunai takes Reiji with him and crosses dimensions to MultiEarth Z2066. Waiting for them there was the Galactic Syndicate Bai Akube, the greatest enemy of the Galaxy Federal Police. In exchange for bringing Reiji with him, Kunai had made “a certain promise” to the leader, Rurugie…!? Soon, Kunai and Reiji engage in a massive brawl within Bai Akube’s impregnable giant fortress. Kunai’s heart is shaken by Reiji’s fearless fighting style…
During a conversation with Reiji and the others, Setsuna begins to wonder if he, as an android, might actually have emotions. “If that’s the case…” he thinks, and tries various methods to see if he can perform the act of crying—something he has secretly longed to do—but since he lacks the structural “tear-shedding function,” he fails every single time. "In that case..." Setsuna heads to the "Gathering of Those Who Long for Tears," where he finds Kunai, who has crossed dimensions to meet the other Gavan. Finally, the samurai and ninja Gavan come face to face, but...!?
Kiki has been kidnapped by someone!? Relying on the Kanky Emorgear left behind at the scene of her disappearance, Kotobuki begins the search. Kunai, who has crossed dimensions to arrive on MultiEarth I5109, also joins the investigation.
Death Gavan suddenly reappears, and Reiji fights alongside Setsuna and Kunai. However, Reiji and the others are no match for his overwhelming strength. Then, Death Gavan deactivates his V-Suit. Tesshin Mikage reveals his true purpose to Reiji and invites him, saying, “Come with me, Infinity”…!?
A series of mysterious building bombings has occurred on MultiEarth A0073. Patran, who has successfully passed Gavan’s tests, is fired up to solve this case and earn himself a major achievement. When he rushes to the scene, he finds not only the First Investigative Division there, but also Reiji and Date from the Records Division for some reason...
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...!?