Upon seeing the Guzzlord that fell out of an Ultra Wormhole, the Masked Royal realizes that this is the Ultra Beast which Ash had previously encountered in an alternate world. Overhearing this, Ash is curious as to how the Masked Royal would know this, prompting the Masked Royal to backtrack and quickly lie, saying Kukui told him. Aware of the dangers posed by Guzzlord, Wicke transforms the stadium viewing box into a communications room. Lusamine takes control of the situation and orders the audience to evacuate Manalo Stadium and make their way over to the port in a calm manner.
The Masked Royal asks for assistance in handling Guzzlord; and Ash, his classmates, Gladion, and Hau volunteer. Suddenly, Team Rocket breaks through the stadium field in their deluxe Bewear robot to steal everyone's Pokémon, not noticing the Guzzlord at first. Guzzlord, however, promptly swats them away with its claw, bringing their stealing scheme to an abrupt end. The four island kahunas also step in, urging the boys to evacuate along with everyone else. Ash demands to stay and tells them Guzzlord's only weakness is the second face above its big mouth.
Team Rocket's mecha stands back up, and the trio uses a rocket-propelled "Double-Edge" missile to latch themselves onto Guzzlord, but it knocks the mecha into the sky. As it descends, Guzzlord opens its mouth wide with the intention of eating Team Rocket. Just then, Bewear, with Stufful on her back, arrives and punches it. Bewear then grabs Guzzlord by the tail and tosses it over the stadium walls, inadvertently taking Team Rocket's mecha with it. The island kahunas are bewildered, but proceed to follow it.
Meanwhile, the Masked Royal and the others help the audience evacuate the stadium, to the ports. Suddenly, Professor Burnet detects signs of another Ultra Wormhole, and Wicke reveals its location - near the shopping mall. Kiawe, Gladion and Hau gather, and witness the Ultra Wormhole opening as a Shiny Guzzlord appears. Gladion promises to hold it off by himself, though Kiawe and Hau refuse, admitting they wish to help him. Meanwhile, at the docks, the evacuation effort is going to plan. Ash prepares to say goodbye to Professor Oak and his mother, assuring them that he and Masked Royal will deal with the situation. Unexpectedly another Ultra Wormhole opens and a second Shiny Guzzlord makes an appearance, landing in the sea below. Ash and Masked Royal rush to face the new threat as it is blocking the evacuation ships from leaving the port.
The black Guzzlord attacks Bewear, who blocks the attack and hits it away, slamming it to the ground. Meowth is impressed by Bewear's power, but Jessie reveals that they might not catch a single Pokémon before Bewear drags them away. So the trio decide to sneak away. As Stufful falls off from Bewear's back, its mother goes to pick it up only for Guzzlord to slam Bewear into a nearby wall. Guzzlord continues bashing Bewear, who is trying her level best to protect Stufful. The Rocket trio are heartbroken by this turn of the event, so they decide to step in to defend their dear friend from further injury. Team Rocket proudly recite their motto for the rampaging Guzzlord. In a complete role-reversal, the trio grab Bewear and Stufful, rocketing them to safety with their mecha. In Team Rocket and Bewear's place, the island kahuna prepare to face Guzzlord.
Meanwhile, Gladion tells Kiawe and Hau that he'll knock the Shiny Guzzlord down before they aim for its weak spot. Gladion's Lycanroc uses Stone Edge to knock Guzzlord off-balance. Kiawe's Turtonator uses Flamethrower and Hau's Decidueye fires a Razor Leaf directly at the second face. Though Guzzlord uses its arms to protect against their efforts. Seeing this, Hau has Decidueye use Spirit Shackle to hold Guzzlord in place, while Kiawe's Turtonator's tries a barrage of Focus Blasts, but both attacks do little and the Spirit Shackle arrows fails to hold. Gladion prepares to activate his Z-Ring, though the three boys are sent backwards by Guzzlord's mighty roar. As Guzzlord steps forward to deal a blow with its claw, Mallow, Lana and Sophocles have their Pokémon fire Magical Leaf, Sparkling Aria, and Zap Cannon which effectively stops the Ultra Beast in its tracks. Lillie rushes onto the scene, as she and her friends brace themselves to deal with this Guzzlord together once and for all.
As the first Guzzlord closes in, Hapu has Mudsdale use Bulldoze to open a hole in the ground, trapping the threat. Olivia's Lycanroc pelts Guzzlord with Rock Slide, followed with Nanu's Alolan Persian's Dark Pulse. Hala orders his Hariyama use Arm Thrust, which only pushes Guzzlord backward. Guzzlord, however, stands right up again and shouts as it readies its claw to strike the island kahuna and their Pokémon. The guardian deities soon appear to address the crisis, using a combined attack to intercept Guzzlord's claw. The island kahunas ask for the Guardian deities’ assistance, admitting they plan to use their combined Z-Moves to send Guzzlord back through the Ultra Wormhole. The Guardians comply, using their combined powers to immobilize Guzzlord. The four kahunas follow through, combining their Z-Moves with Mudsdale's Tectonic Rage sending Guzzlord into the Ultra Wormhole. The kahunas are relieved as the Wormhole instantly closes over. Similarly, Gladion and the others combine their Z-Moves, with the seven-colored rainbow beam of energy blasting their Shiny Guzzlord back into Ultra Space.
At the docks, the Masked Royal calls out his Lucario to distract the remaining Shiny Guzzlord before Ash and Pikachu will attack. Lucario leaps ahead, striking Guzzlord with its Close Combat attack. Pikachu uses Electroweb, which only drapes over the Ultra Beast's head, before Lucario blasts it with a Dragon Pulse. Guzzlord is sent flying backwards and half of its begins to enter the Ultra Wormhole, however it is able to resist the force. Lucario approaches for another Close Combat, but it gets hit by Guzzlord as the Electroweb fades. Ash is coming to realize the strength of this Guzzlord as the Masked Royal recalls Lucario, admitting he doesn’t have any Pokémon that can use Electric-type moves.
Worse still, the Ultra Wormhole seals shut, making the task more difficult than before. Suddenly a giant stinger pierces through the night sky, opening up yet another Wormhole. This time, however, the Ultra Beast emerging from it is a Naganadel. It hones in on Pikachu, who happily leaps into Naganadel's grasp. Judging by Pikachu's reaction and the Ultra Guardians' tag around its waist, Ash quickly realizes that this Naganadel is in fact his Poipole, which has since evolved. Lusamine and her staff are taken aback by the surprising arrival. Ash's reunion is put on hold as Guzzlord rushes in to attack again. Naganadel replies with a Thunderbolt, which stops Guzzlord. At this, Masked Royal suggests it could use Gigavolt Havoc. He reveals his own Electrium Z and asks for Naganadel to lend him its power, to which it complies. Ash and Masked Royal press their Z-Rings, passing the Z-Power to have Pikachu and Naganadel for a devastating double Gigavolt Havoc. Guzzlord tries to counter with its own attack, with the resulting energy wave ripping away Masked Royal's signature mask. The combined Z-Moves manage to overcome Guzzlord's counter maneuver and blasts the Ultra Beast into the open Wormhole. Pikachu and Naganadel cheer at their efforts. Ash turns to thank Masked Royal, but is stunned to see his signature mask is missing, revealing his true identity as Professor Kukui. The Professor only realizes his secret identity has finally been revealed after seeing Ash's reaction, much to his shock.