Overnight, an Ultra Wormhole opens up and a Kartana emerges to look at its new surroundings. The glistening lights of Viren's latest development project, Viren Stadium, instantly attracts the Ultra Beast. As Viren practices for the inauguration ceremony, showing off his gold statue to his his henchmen, he orders a fireworks display. Meanwhile, Kartana promptly slices the statue in half and Viren's henchmen scramble to come up with a solution.
The following morning, Aina's Kitchen is preparing for another busy day of customers. At the same time, the radio announces that the Stufful meteor shower will appear overnight. Mallow prepares to slice up some cabbage when her father asks her to check on the pressure cooker. As she is away, Kartana soars into the restaurant and dices up the head of cabbage into thin pieces. Mallow returns to her work bench to find the sliced cabbage, but Abe is unable to explain anything. Meanwhile, Lillie and Snowy are preparing to leave home for Pokémon School, with Lillie bidding Magearna farewell. Outside, Hobbes is neatening up the hedge trees and plans to make them into Pokémon topiary trees. However, Kartana gets in first and cuts the hedges into geometric designs, shocking both Lillie and Hobbes.
Later, Professor Kukui prepares to teach his class how to use moves to cut objects. Rotom is intrigued by the makiwara and admits that it saw one during an episode of "Alolan Detective Laki". Kukui laughs at the Nogawa reference, admitting that makiwara are often used to practice sword skills. Attempts by Ash, Mallow, and Kiawe fail to fully cut the makiwara, and Professor Kukui admits that even sword masters struggle to cut down makiwara. Ash decides to try again with Pikachu, but Kartana suddenly appears and cleanly cuts through the obstacle with ease before disappearing without being noticed. As everyone else is befuddled, Lillie and Mallow recall their strange experiences that morning.
Suddenly, Komala rings the school bell and the students change into their Ultra Guardians uniforms. In the Ultra Guardians' base, Lusamine and her staff show them a video of Kartana slicing through Viren's gold statue the previous night. Lillie instantly suspects that Kartana is an Ultra Beast, but Professor Burnet admits that she hasn't located an Ultra Wormhole. Wicke adds that Ultra Aura was detected for a moment and Faba affirms that the Aether Foundation is continuing its investigation. Lusamine orders the Ultra Guardians to capture Kartana before further damage is done. The still-multiplying horde of Meltan then present the Ultra Guardians with a box of Beast Balls before they fly out of the base aboard their Ride Pokémon.
Ash orders everyone to split up, and they follow through to cover the entirety of Melemele Island. Suddenly Ash overhears a shrill scream which leads him to the Hau'oli City fruit markets. Anela stares in shock at her sliced fruit. Ash admits that it may be the work of Kartana while Pikachu enjoys a plate of fruit pieces. Meanwhile Lillie attends to Scissors Yoko's salon where Kartana has trimmed and styled her clients' Furfrou into an Alolan Vulpix, Ninetales and Arceus design.
Meanwhile, Deoxys and Rayquaza are in the midst of an intense intergalactic battle. Rayquaza fires a Hyper Beam, but Deoxys transforms into its Defense Forme to protect itself. However the bounced attack strikes a meteor instead, sending it hurtling towards the world.
At Bewear's den, the Team Rocket trio watch Viren on his shopping channel as he advertises the "Bling Bling Gold Safe", a seemingly indestructible safe. Viren orders his Electivire and Pangoro forward to attack the safe with a Thunder Punch and Fire Punch respectively. The safe stands up against these attacks, but Kartana appears and promptly slashes through the safe with ease. Viren orders Kartana to own up to destroying his statue as his Pokémon surround the menace. Meowth is in awe of Kartana's power and Jessie declares that it would make the perfect gift for the Boss.
Soon after, Lusamine alerts Ash and the other Guardians to the latest Kartana sighting, this time at Viren Tower. However, by the time they reach the destination, Kartana has already cut its way to freedom. The Ultra Guardians pursue the Ultra Beast. Lillie suggests they lead Kartana to the mountains to avoid more havoc in Hau'oli City. Kartana readies its blades to slash at the Pokémon School, so Ash and Garchomp fly ahead to intervene. Ash explains that in his world, no one wants anything cut. Kartana appears to understand as it relaxes its blade arms and floats down. Now in the school grounds, Sophocles informs Kartana that they will be sending it back to its home world. Mallow kindly asks Kartana to enter into a Beast Ball, but as Lana throws out the capture device, Kartana slices through it. Seeing as Kartnana is unwilling to be caught, the Guardians settle on battling it. Kiawe calls on his Marowak's assistance. Marowak holds out its bone club and exchanges a stare with Kartana. The tense moment instantly reminds Rotom of sword master Nogawa. Kiawe orders a Flare Blitz. Yet the attack misses and Kartana manages to cut Marowak's Ultra Guardian symbol as a warning.
As the Ultra Guardians gasp in shock, another menace, Team Rocket inside a Meowth robot arrives on the scene. James calls for the cutting Pokémon to come forward before he and his teammates recite their motto. As Team Rocket ends their motto with their classic finishing poses, Kartana sword skills leads the robot to collapse in half. Suddenly Lusamine contacts the Ultra Guardians again, this time to abort the mission for a more pressing matter – one of the Stufful meteor shower's comets is headed directly for them. Faba issues an evacuation order for everyone within a kilometer from the school. Kukui and Principal Samson Oak rush to the Ultra Guardians and inform them that all the other students have been escorted to safety. Principal Oak orders the Guardians to run, but Ash and his classmates declare that they cannot abandon the school. Team Rocket notices the comet quickly approaching, but Bewear arrives before they can enjoy the cataclysm. Bewear throws the Rocket trio into the Meowth robot, crushing the two halves together before re-launching the mecha back to the den.
Ash and the other Guardians use their Ride Pokémon to reach the fast approaching comet. The quickly formulate a plan to rapidly cool the comet to make it brittle before crushing it into smaller fragments. Lillie orders Snowy and Altaria to use Powder Snow and Ice Beam respectively and Lana has Dragonair add its own Ice Beam to the freezing combination. Frost begins to encase the comet so Ash and Mallow have Rowlet and Tsareena use Razor Leaf and Magical Leaf. Kiawe and Sophocles follow up with a Slash attack from Charizard and Metang tries a Metal Claw. However the efforts only destroy the ice surrounding the comet and it continues to descend towards the school. Kartana decides to take up the challenge. It soars upwards and it cuts the comet into smaller fragments. The remnants make a landing in the nearby ocean and the resulting splash makes a rainbow appear in the sky overhead. Kartana notices the rainbow and prepares to slice it as well, but Sophocles admits that even it can't cut a rainbow. Lusamine makes an urgent call through to the Ultra Guardians and is instantly relieved to see that they are uninjured. Burnet scolds them for making such a rash move, before adding her gratitude. Everyone's attention soon averts to a newly opened Wormhole, courtesy of Kartana's own sword mastery. Burnet and the others are mildly impressed, and Kartana's display adds more information to the Aether Foundation's Ultra Beast database. As Kartana leaves the Alola region for its Ultra Space home, the Guardians all thank Kartana for its assistance.
