Ash and his classmates join all of the other Alola League participants on the Manalo Stadium battlefield. Among the contestants are Oluolu, Master fisherman, Mina, Kahili, and Acerola, the last of which surprises the group with her presence. Jessie and James are in disguises, planning to get through the preliminary round by avoiding the battles at all costs. The one most favored to win, Ilima, makes his way into the stadium, where he is greeted by his many fans, much to the annoyance of Tupp. Plumeria orders all of the Team Skull Grunts to not get in the way of Guzma's victory.
Professor Kukui greets the League participants and the crowd and declares the Manalo Conference to be open. Caster takes over, declaring his role as the announcer. He introduces the Manalo Conference's official judges, which are all four island kahunas: Olivia, Hala, Hapu, and Nanu. Caster then explains that 151 contestants will be competing for the title of Alola Champion. They will be whittled down to the Top 16 in a series of Battle Royal-style matches. Soon, the participants get into their starting positions, spanning the entire perimeter of the battlefield. The island kahunas raise their hands and a countdown begins, with all of the Trainers calling out their respective Pokémon partners.
The countdown reaches zero and the preliminary round officially begins, kicking off the Manalo Conference. Hiroki rushes out with his Mudbray, ordering any challengers to come at him. However, he and Mudbray are immediately struck by a combination attack, making him the first to be knocked out of the competition. Pikachu lands an Iron Tail on a Sudowoodo's forehead, which causes it to immediately faint. As Ash cheers for his early victory, Kiawe orders him to pay attention to the fast-approaching Poliwrath. Pikachu launches an Electroweb attack to defeat Poliwrath, also knocking out a nearby Araquanid in the process. Meanwhile, Kiawe's Turtonator takes a direct Flamethrower from a Salamence, before striking it away with a Dragon Tail. Lillie joins the scuffle, and has Snowy freeze Salamence with a Powder Snow, taking the Dragon type out of the fight. Sandy and Shaymin quickly defeat three opponents, with Lana and Mallow congratulating them. Sophocles has Togedemaru bowl a Shiinotic out the way with Zing Zap. A Politoed leaps and grabs Togedemaru, but it is quickly defeated by Togedemaru's newly learned Spiky Shield. From a sky-box, Wicke sees Faba defeating a competitor's Boldore with his Alakazam.
As 79 participants remain, Ash and Pikachu face off against an intimidating Gyarados. As Ash prepares to call out an attack, a Skarmory swoops in and uses Metal Claw on Gyarados. Pikachu then uses the opportunity to leap onto Gyarados and deliver a direct Thunderbolt, knocking both Skarmory and Gyarados out with one hit. Kiawe orders Turtonator to keep an Alolan Sandslash at bay with a Flamethrower, though it continues to spin closer. Kiawe switches tactics and calls for Turtonator to use Shell Trap. The maneuver catches Sandslash off-guard as its claws directly touch Turtonator's spiny shell, setting off the Shell Trap and defeating the Mouse Pokémon. A tense standoff between a Magikarp and a Pyukumuku abruptly ends due to an Electro Ball from Pikala's Pikachu, Bolt. However, Pikala's victory is short-lived, as Jessie's Mimikyu knocks Bolt out with a Shadow Ball. Mimikyu then runs for another Trainer's Pikachu, leaving Jessie and James overwhelmed.
As 65 participants remain, a Talonflame swoops towards Gladion and his Silvally, though they evade the attack. Gladion throws a Rock Memory to Silvally, transforming it into a Rock Pokémon. After Talonflame is quickly taken down by a super-effective Multi-Attack, Gladion and Silvally spot Ash and Pikachu sitting on the battlefield. The pair exchange stares before Gladion warns Ash of an incoming attacker, a Primeape, while a Clawitzer leaps up behind Silvally. Pikachu leaps into action, using Thunderbolt to defeat the Clawitzer as Silvally lands a Crush Claw on Primeape, taking it down. Gladion tells Ash to not lose in the preliminaries, and Ash offers him the same advice. The two rivals go their separate ways as they rush back into the melee.
Kiawe goes up against Mad Magmar and Mr. Electric as Viren, sitting in the stands nearby, orders his minions to teach him a lesson. Turtonator starts off with a Flamethrower, though the attack fails to do any damage to Magmortar. Mr. Electric orders his Electivire to use Thunder Punch. Turtonator, however, uses Shell Smash and easily avoids the attack with its now-boosted Speed, before defeating both Magmortar and Electivire with a single Dragon Tail. Viren is in shock as Olivia officially declares the pair unable to continue.
With 34 Trainers now remaining, the crowd's attention turns to Ilima, who has his Eevee unleash an overwhelming Last Resort attack, which defeats all of the Team Skull Grunts with one hit. Ilima is then immediately faced by Plumeria, who tells her Salazzle to use Sludge Wave. Ilima has Eevee use Quick Attack to leap over the attack and to Salazzle's position. Salazzle lashes Eevee with Dragon Claw and follows up with Dragon Pulse. While Eevee manages to evade much of the Dragon Pulse, one of its back legs is injured. Despite this, Eevee performs another Quick Attack to get away from another Dragon Pulse. With enough distance, Ilima has Eevee use Swift, striking Salazzle out of the competition. Plumeria, however, is not disappointed by her effort, admitting that she already did what she came to do. Eevee limps over to Ilima, its condition instantly concerning him.
Later, Kukui watches from the grandstand as Guzma continues defeating opponents, concerned that the Team Skull leader's clearance of the preliminaries may jeopardize the Alola League's future. With seventeen contestants remaining, only one more Trainer has to be eliminated before the round can mark its end. Jessie's Mimikyu confronts Ash's Pikachu, who uses Electroweb to block its oncoming Shadow Ball, leading to an explosion. James yells at Jessie to abandon the battle so they can both get into the next round. At that moment, Kiawe's Turtonator defeats another Trainer's Metagross with an Inferno Overdrive, concluding the preliminary round. Mimikyu, however, doesn't care and continues to attack, forcing Jessie to recall it back into its Luxury Ball. Jessie runs over to James, relieved to have just qualified for the next round. All of the qualifying participants are soon revealed, including Ash, all of his classmates, Jessie and James, Mina, Acerola, Ilima, Gladion, Faba, Samson Oak, Guzma, and Hau.
Overnight, the group stops off at the League Pokémon Center to have their Pokémon healed up from the day's intense matches by the gathered Nurse Joys of Alola. Ilima urges his injured Eevee to take it easy, though it seems disappointed that it still needs to recover. Shortly after, Caster appears on the Pokémon Center television screen to announce the next round's pairings. Ash and Faba are revealed to be the first pair, making Ash happy to be the first one to battle, while Faba starts thinking about plans to use against Ash. The next pair is revealed to be Ilima versus Guzma, to which the Team Skull Boss responds with a satisfied smirk. The third match is Hau versus Samson Oak, and Hau is determined to win. The fourth battle is revealed to take place between Mallow and Lana, surprising the two childhood friends. As Sophocles learns that he'll be facing Mina in the fifth battle, he gets all nervous. In their van, Jessie and James follow the announcement as well and are shocked to see themselves in the sixth pair, meaning that only one of them has the chance of advancing past the first round. The seventh battle is revealed to be between Kiawe and Acerola, making Kiawe express his usual fiery confidence. And finally, the eighth battle is revealed to take place between Lillie and Gladion, making Lillie surprised that she's going to face her big brother. With all the match-ups revealed, Ash calls for everyone to give it their all, and his classmates respond back with a resounding cheer.