Ash and his classmates are aboard a ship bound for Manalo Stadium, the venue of the upcoming Manalo Conference. Lillie surprises her friends with an outfit change to represent her more confident self. Ash promptly leads everyone into a cheer for the conference. Now docked, Professor Kukui greets his students. Ash is particularly keen to see the battlefield, but Kiawe reminds him that they haven’t even signed up yet. Kukui adds that registrations end by the evening and he suggests they tour the island in the meantime. He leaves the children to their own devices while he continues to prepare for the League festivities. Ash is set on seeing the battlefield, and the other boys follow after him. However the girls are keen to do some shopping and settle on the mall.
Meanwhile, Team Rocket sets up their van in preparation for the swells of League spectators. James remarks that their early-release Manalo doughnuts were a success, but Jessie pulls his enthusiasm into line and reminds him that they need to be focussed on winning the Alola League to conquer the Alola region. Meowth remarks that they can get rich while selling doughnuts and still win the League. Jessie suddenly notices a Stufful walk into her line of sight, causing the trio to enter into a frantic search for its mother, Bewear. However, this Stufful is revealed to belong to a spectator. James and the others collapse out of relief. He admits that they made all preventative measures to avoid Bewear interrupting their plans, namely constructing a relaxing hot spring for Bewear to enjoy.
Ash and the boys reach the Manalo battlefield and are impressed by its grand scale. Hau rushes over to greet Ash, and he declares that he will be entering the League as well. Hala arrives on the scene, to which Ash explains that Hau is Hala's grandson. Kiawe and Sophocles introduce themselves to Hau. Though Ash instantly notices his sparkling new Z-Ring, and hau explains that he finally cleared his grandfather's grand trial. As Hau boasts, Hala is quick to remind his grandson that he only begun his island pilgrimage. Hau also reveals that his Dartrix has since evolved into a Decidueye. Ash shakes his backpack to retrieve Rowlet, but it is fast asleep. Hau then spots Meltan who is also sleeping. Ash tries to shake Rowlet awake, but it is Decidueye's pecks that wake it up. Rowlet and Decidueye are thrilled to see each other again and exchange a secret handshake. Hau decides to explore the Manalo Stadium island with Ash and his friends, with Decidueye and Rowlet soaring into the sky.
Meanwhile, the girls are in awe of all of the stores. Lana suggests they go for some Berry Juice drinks. Mallow approaches the counter to order, but she is shocked to see that the attendant is actually her older brother, Ulu. He explains that he decided to return to Alola for the opportunity to open a pop-up store, and Mallow replies that she is entering the League. Ulu is thrilled by the news and admits that he'll close up the store to watch his sister's battles, though Mallow slumps over at her brother's enthusiasm.
Team Skull are also on the scene, however Tupp is keen to gatecrash the Manalo Conference. While his fellow grunts aren't keen on the secretive plan, namely because Guzma has not ordered it, Tupp is set on it. He explains that the plan will thrill their boss as Guzma dislikes Kukui, and reminds them all of Guzma's earlier statement about the League. Rapp asks for more details and Tupp orders the grunts to just do stuff. Later, Officer Jenny causes Tupp and his teammates to scatter during some graffiti on an advertising poster. Lillie and the others approach Jenny, and she explains that some troublemakers have been littering and picking fights with the visitors. As Officer Jenny leaves to continue her patrol, Mallow and the others declare they'll intervene if they come across any troublemakers.
Team Rocket's sales are interrupted when a Team Skull Grunt skips the line. Jessie is determined to not create a scene so she kindly asks the grunt to join the queue. The grunt persists to ask irritating questions and kicks over an advertising sign, causing the waiting customers to flee. Two others grunts soon join him. With the situation heating up, James calls on Mareanie to join Meowth and Wobbuffet in a show of force. However the grunts call on their Pokémon, but the Rocket trio quickly defeats them. Gladion and his Lycanroc quickly deal with another troublesome Team Skull trio.
Later, Ash and the boys interrupt Tupp and his gang's small crime spree. Tupp is initially startled, but is set on getting her revenge against them so he orders Zipp and Rapp on the attack. Ash sends Pikachu and Rowlet out, Kiawe's Turtonator, Sophocles's Vikavolt and Hau's Decidueye also enter the fray. The Team Skull trio reply with Garbodor, Zubat and Salandit. Zipp's Garbodor sends out a Sludge Bomb, but Turtonator destroys the oncoming attack with a Flamethrower. Tupp orders his Salandit to use Scratch, though Rowlet’s Seed Bomb knocks him to the ground. Zubat swoops in for a Bite. Hau has Decidueye evade the attack and defeat Zubat with a Razor Leaf. The battle has been won, though Sophocles is left disappointed that he wasn't even able to attack. Ash and others demand to know what the grunts want, and Rapp replies that the League should just burn.
Guzma and Plumeria walk onto the scene, causing Tupp and his gang to scramble up to their bosses. Plumeria scolds the trio for running off and brushes off their attempt to hijack the League as beyond useless. As Guzma prepares to call out a Pokémon, the girls, Hala and Kukui rush in. Kukui confronts Guzma demanding to know why he is at the League. Guzma replies that Kukui was the one who told him to enter the League in the first place. He affirms if his registration will be confirmed. Kukui replies yes and Guzma declares that it will be a regrettable decision once he dominates the arena. Guzma vows to ruin Kukui's dreams, declaring that when he is Champion he'll ensure that no more Leagues will ever take place. He staunchly leaves with Plumeria, Zipp and the others following behind. Guzma's threats hit Kukui hard. Lillie asks the Professor why Guzma is so obsessed with him, but Kukui only stares at her before returning to his distraught state. Hala proceeds to inform the children that Kukui and Guzma were once his apprentices. However Guzma was particularly disobedient and had no regard for the traditions of the island challenge. He ran off hoping to prove his strengths without the need for either a Z-Ring or Z-Crystals. Hala admits that he failed to save Guzma's heart, but Kukui feels that the responsibility lies with him. Ash is set on winning the League, namely to defend Kukui's efforts and all of the nice people he has met in Alola. Hau and the others agree with Ash’s sentiments, admitting that they don’t want Guzma to squander the League. Kukui stands to his feet and thanks everyone for their support.
Overnight, Kukui presents the competitors with a League eve feast. Ash and his friends call out their Pokémon to enjoy the meal. They soon spot Principal Oak in an Alolan Exeggutor costume, and are even more surprised to learn that he is also competing in the conference. The screaming girls alert the group to Ilima's presence. As Ash goes to greet Ilima, he is bowled over by some of Ilima's fans. Gladion reveals that he will be participating, while Guzma and Plumeria are also seen in the crowd of competitors. Later, Kukui ushers everyone over for a presentation about the preliminary round rules, presented by the Masked Royal via a television screen. He explains that the participants will compete in a free-for-all, where only the final 16 left standing will advance onto the final tournament, a Battle Royal.
