A mysterious space sage entrusts Yuma with challenges that surpass the limits of his imagination with a stake too high. He asks, "Should you fail… then you… will lose your power as Arc." The burden of protecting Hoshimoto City alongside SKIP members are twisted by Sascal, who manipulates them, sending challenge after challenge toward Yuma. Battling giant kaiju, an evil alien bent on destruction, and a warped dimension where even time itself is distorted, Yuma must confront the ultimate test. Will he... will Ultraman Arc overcome the greatest challenge yet and protect the future, surpassing the limits of the power of imagination?
A wave of kaiju emerges from an industrial zone, prompting Capitan Gento and the SKaRD to engage in the relentless battle. Yet despite their efforts, the endless kaiju attack continues. Suspecting a link to Necromass Co., an advanced chemical company that researches kaiju carcasses and owns factories in the industrial zone, SKaRD rushes to the company’s CEO and renowned chemist, Dr. Mabuse. At Necromass Co.’s research facility, Dr. Mabuse explains the development of the damudoxin, a substance on the brink of achieving immortality. Meanwhile, Alien Damuno, who claims themselves as the “ruler of the universe” appears! Chaos ensues when damudoxin leaks from the destroyed tanks, consuming samples of kaiju carcasses and giving rise to the giant Gongilgan, the Demonic Carcass. Set in Tokyo, the capital of Japan, Ultraman Blazar and SKaRD clash in a showdown against the giant kaiju!
When GUTS-Select investigate mysterious disappearances, they learn it is work of an evil alien who intends to invade the Earth, called Professor Gibellus. However, just in time, a mysterious woman appears to help GUTS-Select.
Zero finds himself trapped within a universal gap and faced against an impostor Ace. Following the battle, Darklops Zero was restrained once more by Herodia, remembering a figure named "Kaiser Belial" before deactivating. Rei was restrained after his failed attempt to intrude the alien base but was rescued by none other than his alternate self. Unlike the prime Rei, alternate Reimon was never able to control his powers, forced into the state of Reionic Burst until the original Rei punched Reimon, thus deactivating its Reionic Burst mode. Rei revealed that he lost his Rayblood instinct after Hyuga threw Seven's Eye Slugger, creating a scar on his chest which symbolizes the former's friendship with ZAP SPACY members. While searching for Rei, Hyuga instead finds his Neo Battle Nizer and an entrance to the alien base made by Litra. Although the fake Ace was destroyed, Zero try to find an escaped but was halted by Seven and Ultraman impostors.
Zero sits on a cliff while he watches a strange tower firing lightning bolts, and then rises to face against what it seemed to be members Ultra Brothers, Ultraman, Robot Zoffy, Ultraman Jack and Ultraman Ace. After incapacitating the ZAP SPACY's Space Pendragon, Ultraseven joined the group as they face against Zero.