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 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 cover the entirety of Melemele Island. Suddenly, Ash overhears a shrill scream, which leads him to the Hau'oli City fruit markets. There, he finds Anela, who is staring in shock at her sliced fruit. Meanwhile, Lillie arrives at Yoko's salon, where Kartana has already trimmed and styled her clients' Furfrou. At the same time, Deoxys and Rayquaza are locked in battle in space. Rayquaza fires a Hyper Beam, but Deoxys transforms into its Defense Forme to protect itself. The deflected attack strikes a meteor instead, sending it towards the planet below.
At Bewear's den, Team Rocket watches Viren on his shopping channel as he advertises the "Bling Bling Gold Safe", a seemingly indestructible safe. Viren orders his Electivire and Pangoro to attack the safe with Thunder Punch and Fire Punch, respectively, to no effect. Just then, Kartana appears and slashes through the safe with ease. Viren recognizes Kartana as the one who destroyed his statue and demands that it own up to its deeds as his Pokémon surround the Ultra Beast. 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 others to the latest Kartana sighting, this time at Viren Tower. However, by the time they reach it, Kartana has already cut its way to freedom. During the pursuit, Lillie suggests leading Kartana to the mountains to avoid more havoc in Hau'oli City. Just then, Kartana prepares to attack the Pokémon School, forcing Ash and Garchomp to intervene. Ash explains no one wants anything cut in his world, which Kartana appears to understand. With the Ultra Beast placated, Lana throws out a Beast Ball, but Kartana slices through it. Realizing Kartana is unwilling to be caught, the Ultra Guardians battle it. Kiawe sends out Marowak and orders it to use Flare Blitz, but the attack misses. Kartana then manages to cut Marowak's Ultra Guardian symbol as a warning.
Just then, Team Rocket arrives inside a Meowth robot. Right after Team Rocket ends their motto, Kartana is revealed to have sliced the robot in half already. Lusamine contacts the Ultra Guardians again, this time to abort the mission because one of the Stufful meteor shower's comets is headed directly at them. Faba issues an evacuation order for everyone within a kilometer of the school. Principal Samson Oak orders the Ultra Guardians to run, but Ash and his classmates declare they will not abandon the school. Team Rocket notices the comet quickly approaching, but Bewear arrives before they can enjoy the cataclysm. Bewear throws the trio into the Meowth robot, crushing the two halves together, and launching the mecha back to the den.
Ash and the others use their Ride Pokémon to reach the comet. They decide 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, while Lana has Dragonair add its own Ice Beam. As frost begins to encase the comet, Ash, Mallow, Kiawe, and Sophocles's Pokémon follow up with their own attacks, but their efforts only destroy the ice and not the comet. Kartana then soars upwards and cuts the comet into smaller fragments, which land in the ocean and cause a rainbow to appear in the sky. As Lusamine and Burnet check on the Ultra Guardians, Kartana opens up a new wormhole by itself with its slicing abilities and uses it to leave the Alola region.