When Ash's group went after a Pokémon upon getting off the Pokemon Taxi ride, they entered a forest. Along the way, they all first encountered Bewear, and Ash, Serena and Sienna waved and called it cute, but their opinion changed immediately once they saw it smashing down various tall trees in joy. As the Pokémon then approached them for a hug, Ash and his friends rushed off in the opposite direction, but it began to chase after them, coming close to catching them until it was distracted by the mysterious Pokémon from earlier. Ash's group and their Pokémon companions, after escaping the rampaging Pokémon, spot a Charizard in the air and decided to follow it.Emerging from the forest, Ash and the gang arrive at a area with a huge building. They spotted a girl next to some new Pokémon, so Ash jumped over the fence and headed towards them, but the girl warned Ash to look out as, unknowingly to Ash, various Tauros being ridden by Trainers head straight for him, but before he could get out of the way, they all crash into him. One Trainer ordered her Tauros to stop, but it was too late as Ash had been trampled by the Tauros. The girl rushed over to Ash to ask how he was, to which Ash told her that he was used to Tauros as he had caught some before. As one of the Tauros approached Ash and the girl, only for the latter to back off in fear. It was revealed by a boy that Lillie is scared of Pokémon and can't touch them. After recognizing the girl who was fishing earlier, Ash and the gang were informed that they were at the Pokémon School and were shown around. Right then, however, an Alolan boy who looked like Ash showed up at the entrance. Serena looked at Ash and his 'look-alike' and asked the latter who he is. The boy introduced himself as Iakopa Kekoa and says he's glad to have finally met Ash. Confused, Ash asked why. In reply, Iakopa revealed that his father is Trey's twin brother! Shocked to hear this, Ash, Jason, Ashley and Flare instantly realized that Iakopa is their Alolan cousin.
When they were shown around, the group met the cousin of Cilan, Chili and Cress, known as Corbin, who told them the names of the people Ash just met, including the girl showing them around being named Mallow. As Ash, his friends and Mallow were looking around the school, Ash's group was brought to the principal's office, being mistaken as new students, but as Ash tried to clear things up, he, Jason, Ashley, Flare, Serena and Sienna saw Trey and Delia and they and the rest met the school's principal, Samson Oak, Professor Oak's cousin. The meeting left Ash and the gang stunned as they learned of Samson's habit of making jokes using Pokémon names. Inside the office, Ash and the gang cleared things up with Mallow, whose habits Corbin was always easily annoyed at, as Samson calls Professor Oak to tell him he had received the egg safely, to which he thanked Delia. Mallow asked Samson if she and Corbin can show Ash and the gang around the campus and showed Ash to the classroom first. Ash and the gang were introduced to the class teacher, Professor Kukui, who welcomed them happily.
Soon, Ash and his friends saw a boy and his Charizard approached by a gang of people. They learned that they're part of a group known as Team Skull, who bully people into battling them. One of the Team Skull members made a deal that the boy could leave if he would win their battle, but if he would lose, they would get his Charizard and send out their Pokémon, Yungoos, Salandit and Zubat to begin their battle, ordering him to tell Charizard to fight. Just then, Ash, Serena, Sienna, Jason, Ashley, Flare, Sora, Riku, Kairi, Felicia, Madoka, Homura, Ciel, Neros, Mimi, Kura and Burke step in to confront the group, telling them how unfair the battle was and joined the battle themselves, introducing themselves to the boy, who introduced himself as Kiawe, but told Ash he doesn't need any help. As Ash sent in Pikachu and Greninja, Jason sent in Pika, Charizard, Squirtle and Ivysaur, Ashley sent in Pinkachu and Bayleef, Serena sent in Braixen and Sylveon, Flare sent in Feraligatr and Houndour, Neros sent in Pikavolt, Dewott and Grovyle, Mimi sent in Lucario, Buizel and Torchic, Sora sent in Excalibur and Emboar, Riku sent in Sandslash and Highwind, Kairi sent in Fireflower and Delcatty, Felicia sent in Persian and Glameow, Madoka sent in Raichu and Espeon, Homura sent in Shiny Umbreon and Mega Absol, Ciel sent in Darkrai and Mega Houndoom, Kura sent in Marill and Burke sent in his Shiny Geodude, Kiawe sent out his Turtonator, and revealed that it is a Fire and Dragon type, and also a trusted friend of his. After that, Corbin steps in and sent out Panshock. The members of Team Skull command their Pokémon to use Venoshock, Bite, and Leech Life respectively, but Pikachu successfully dodged the Venoshock with Quick Attack, as Kiawe commented on Pikachu's speed. The Yungoos and Zubat bit down on Turtonator's shell, causing an explosion from the sensitive spines on Turtonator's shell. Salandit was ordered to use Flame Burst, but Ash told Pikachu to dodge and use Thunderbolt, with Jason's Pika, Ashley's Pinkachu and Neros's Pikavolt and Corbin's Panshock using the same attack to add to the shock, which connected with the three Salandit, which impressed the students, as well as Kura, Burke and the mysterious Pokémon watching from a tree.
Kiawe told Ash, his friends, Iakopa, Corbin to leave the rest to him as he powered up his Turtonator using a crystal on his wrist, which allowed his Turtonator to use a move known as Inferno Overdrive, which was strong enough to defeat the villain's Pokémon at once, causing them to retreat. Ash asked Kiawe what he just did, but Professor Kukui stepped in to explain that they're known as Z-Moves, which are moves passed down in Alola after completing the island challenge on the four islands of Alola. Ash got excited by all the things he had just learned, but suddenly saw a flying Pokémon, and once describing it to the group, they, Burke and Kura identified the Pokémon as Tapu Koko, the guardian of Melemele Island.
Later that night, Ash, his siblings, Neros's gang, Serena, Sienna, Sora, Riku, Kairi, Felicia, Madoka, Homura, Ciel, Sebastian, Kura, Burke, Trey, Delia, Pikachu, Pika, Pinkachu, Pikavolt, and Mimey were enjoying a meal at a restaurant. Trey and Delia commented on the food, but Ash was thinking about everything that had happened earlier, which was noticed by Trey and Delia as they asked him if there was anything that happened to distract him. Ash and his friends then heard a noise echoing and recognized the Pokémon in a tree, leaving the restaurant and immediately chasing after it. Searching around, they encountered it again, following and meeting it at a viewing point where they remembered it as Tapu Koko received an object that he recognized as what Kiawe was wearing. After approval from Tapu Koko, Ash put the object on his wrist before watching Tapu Koko fly off away from him and his friends. Ash and the gang then stared at the Z-Ring.
The next day, Ash, his siblings, Serena, Sienna, Neros's gang, Kura and Burke were at Professor Kukui's house talking to Trey and Delia, who were back in Pallet Town, over the video phone. Ash and the gang then remembered that they started their first day of Pokémon School today and hurried off after saying goodbye to Trey and Delia. As Ash raced up the road with Pikachu and the others, they all look out to the ocean before they all had a race to the Pokémon School campus. Since then, they've been on tons of adventures together alongside their classmates, including Corbin.