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. Few know his true purpose: investigating trans-dimensional Emorgear crimes. Reiji now heads for "MultiEarth Λ8018," where an Emorgy Negative Wave threatens to expand across dimensions and potentially collapse the entire universe. Amidst Λ8018's chaos, he encounters Setsuna Aikokuin, captain of the Galaxy Federal Police's Special Forces, but...!

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... To silence the arrested Hitoshi Kuzumi, the crime syndicate's boss, Karasumaro, attacks Setsuna and his team. As one incident follows another, Setsuna sees Reiji burning with rage toward Karasumaro and...!

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. As the trio sought the truth behind the incidents, a new Emons attacked them, and Kiki transforms into Gavan Luminous!

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. Soon, Reiji and his team arrive at a mysterious underground fortress, only to be attacked by the culprit's drill machine and find themselves in a pinch...!

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... Conflicted, Setsuna reunites with Reiji, who has crossed dimensions, and is entrusted with something. As the two fight together once more, the secret behind Setsuna's dual-wielding style is revealed...!?

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. In the midst of the chaos, an Emorgear goes haywire, putting Emu in grave danger! With Reiji crossing dimensions to lend a hand, will Kiki and Koto be able to save Emu...!?

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...!? Reiji, who has been harboring anger for quite some time, fights Death Gavan even as he is battered and bruised...!

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. As the investigation progresses, an Emons attacks and Setsuna transforms, but the sniper’s bullet targets Gavan Bushido…!!

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. Just then, another emergency arises. To save Kiki, who is acting strangely—unlike her usual self—Kunai transforms into Gavan Raiya and unleashes a surprising new ninja technique!