Magic gates appear throughout Japan, causing havoc as people are instantly transported from one place to another. While investigating the situation, Haruto SomaIcon-crosswiki and KoyomiIcon-crosswiki are approached by Geki JumonjiIcon-crosswiki, who suddenly attacks Haruto after confirming his identity. Geki and Haruto fight as Space Sheriff Gavan type-G and Kamen Rider Wizard until Kamen Rider Wizard and Koyomi risk themselves to save a passerby from being hit by collateral damage. After confirming that both are good people, he stays his blade and flees. Meanwhile, Yoko UsamiIcon-crosswiki from the Go-BustersIcon-crosswiki and her BuddyloidIcon-crosswiki Usada LettuceIcon-crosswiki are camping beside a river until an unknown object falls from the sky beside them. They find a small robot at the crash site, which Yoko takes to the Energy Management CenterIcon-crosswiki and fixes it up. The robot introduces itself as PsycholonIcon-crosswiki and she becomes friends with it.
Meanwhile at the Galactic UnionIcon-crosswiki, Geki confronts his superior and the previous Gavan, Retsu IchimonjiIcon-crosswiki, about his orders to eliminate both Kamen Rider Wizard and Kamen Rider Beast, Kosuke NitohIcon-crosswiki, but Retsu insists that both are too dangerous to be allowed to live because of their magical powers. Retsu relieves him from duty, sending the Space Sheriff SharivanIcon-crosswiki to complete the task. Back at the location where Yoko found Psycholon, monsters from the evil organization Space ShockerIcon-crosswiki are confronted by Kamen Rider Wizard until they send him away using a magic gate. Haruto emerges at a stadium where he is encountered by the KyoryugersIcon-crosswiki who mistake him for a Debo MonsterIcon-crosswiki at, then challanged by Kyoruger’s Daigo KiryuIcon-crosswiki to ddetermine how brave Haruto is until Gai IkariIcon-crosswiki from the GokaigersIcon-crosswiki appears to stop their fight as he wants to meet with Haruto about the incident of Space Shocker’s plan of framing Haruto using a same magic power. Geki attempts to stop Sharivan from leaving to Earth to execute Kamen Rider Wizard and Kamen Rider Beast with no success. Yoko is attacked by Space Shocker, who are after Psycholon, but her fellow Go-Busters Hiromu SakuradaIcon-crosswiki and Ryuji IwasakiIcon-crosswiki appear to assist her. When the monsters try to send both Yoko and Psycholon through a portal, Hiromu and Ryuji appear to save her and are sucked in instead, and she is forced to keep fighting by herself.
Gai and Haruto discuss the situation, later joined by Geki and Nito, until Sharivan appears to fight them. To dissuade his fellow Space Sheriff, Geki tries to don his combat suit with no success and his partner ShellyIcon-crosswiki informs him that after he was removed from duty, the Dolgiran’sIcon-crosswiki systems were locked down, preventing her from providing him his weaponry. When monsters from Space Shocker also appear at the scene, Sharivan is forced to stop pursuing the other heroes to fight them until they flee through a portal leading to the Genmu WorldIcon-crosswiki and Geki also dives there by himself to investigate. Past the portal at the Genmu CastleIcon-crosswiki, Geki witnessess Strategist RaiderIcon-crosswiki from the Space Crime Syndicate MadouIcon-crosswiki and Shadow MoonIcon-crosswiki discussing their plan to use Psycholon to gather enough magic energy to revive Madou’s leader Demon King PsychoIcon-crosswiki, learning that they are the ones behind Space Shocker. Soon after, Gai appears to help Geki escape, and back on Earth, they rescue Yoko and Psycholon from Space Shocker troops. Taking refuge at the Antique Shop OmokagedōIcon-crosswiki with the others, Geki reveals that the Galactic Union intends to destroy Earth with the Super Dimensional CannonIcon-crosswiki to prevent Space Shocker from completing their plan, as their scheme threatens the entire universe.
Encouraged by Gai and the others to not give up yet, Geki leaves to confront Space Shocker by himself until as Kai/Sharivan appears to that the evidence of the villains who framed Wizard and Beast of using a same magic power has been informed as the villains is on the moves to revived Madou and inform him that they have one hour until the Galactic Union fires their main weapon to destroy the Earth, then leaves to call Shaider for reinforcement. While Gai seeks help, Geki enters the portal to the Genmu World, accompanied by Yoko, Psycholon, and Nito, and they are attacked by Space Shocker. Separated from the others, Geki is forced to confront the monsters unarmed until Kotoha HanaoriIcon-crosswiki from the ShinkengersIcon-crosswiki appears at the Dolgiran, revealing that she was sent there by Gai. She hacks the ship’s systems to lift the lockdown and allow Geki to transform into Gavan type-G once more. Yoko keeps pushing forward by herself until Reider and Shadow Moon appear to block her path and attempt to take Psycholon from her, and the little robot uses its powers to have her reunited with Hiromu and Ryuji. Just as Kamen Rider Beast and Gavan type-G are about to be defeated, several Kamen Riders and Super Sentai warriors, including another hero’s Sangiman/new Inazuman appear to help them. Gai rejoins his fellow Gokaigers and Gavan type-G provides them with six Metal Hero KeysIcon-crosswiki to assist in the fight.
The Go-Busters have a tough battle against Shadow Moon until the Gokaigers, Gavan, Kamen Rider Beast, Kamen Rider Wizard, Sharivan, Kamen Rider FourzeIcon-crosswiki, and Kamen Rider MeteorIcon-crosswiki appear to assist them, joined by ShaiderIcon-crosswiki, Kamen Rider OOOIcon-crosswiki and the Kyoryugers also join the fight as well. As Shadow Moon and his reinforcements are defeated, the one-hour delay provided by the Galactic Union runs out and a regretful Retsu is forced to fire the Super Dimensional Cannon. The three Space SheriffsIcon-crosswiki then ride their ships and manage to stop the weapon’s blast from hitting the Earth but Reider reveals that it was their intention all along to use its energy to complete the Demon King’s resurrection. The resultant explosion provides enough power for it, before Reider perishes, just to later return as Space Reider, bringing several other monsters to the fight. Psycholon is also overcome by the energy surge and is put under Madou’s control as well. The heroes find themselves in a pinch against their enemies until AkarangerIcon-crosswiki and Kamen Rider 1Icon-crosswiki arrive with reinforcements. Kyoryu GoldIcon-crosswiki appears to assist Kamen Rider Beast against Space Reider and together, they destroy him for good. Yoko calls out for Psycholon and it manages to break free from Psycho’s control but ends up sacrificing itself to protect her from a fatal blast. The enlarged Psycho tries to escape into space, but Gavan type-G, Sharivan, and Shaider, who revealed to be alive appear to stop it, and the monster is ultimately destroyed by a robot formed by the Kyorugers’ KyoryuzinIcon-crosswiki and Kamen Rider Wizard’s WizarDragonIcon-crosswiki combined. After the battle, Usada reveals to Yoko that Psycholon can be fixed, and as the Space Sheriffs return to space, the Kamen RidersIcon-crosswiki and Super Sentai warriorsIcon-crosswiki bid their farewells after they had joined forces to protect Earth once more.