At the Pokémon School, Ash's classmates are playing with their Pokémon. Lana tells her Popplio to make a balloon, which pops, while Sophocles puts Togedemaru in a wheel to charge his computer program. Meanwhile, Lillie walks up to Mallow and recommends to her that she should add some berries to the Pokémon food in her new recipe. However, as Mallow thanks Lillie for the suggestion, Bounsweet jumps up in front of Lillie, scaring her frozen on the spot. Mallow comments that it is a shame that Lillie is afraid to touch Pokémon, to which Lillie denies. Kiawe walks in, feeling tired after making a delivery to Ula'ula Island. Professor Kukui then enters and greets the class, with Ash and Pikachu behind him. Kiawe notices the new Z-Ring that Ash is wearing. Professor Kukui reveals that Ash will be a student in the Pokémon School and tells the class not to hesitate to help him out with any questions that he has. Ash introduces himself to his new classmates and his intention of becoming a Pokémon Master, saying he is glad to be here.
Soon afterward while Ash is talking to his new classmates, Sophocles and Mallow notice the Z-Crystal on Ash's Z-Ring, with Kiawe identifying it as an Electrium Z. He asks where Ash got it, as he has not taken part in any trial of the island challenge. Ash explains that Tapu Koko had given it to him, which surprises the class. Ash then explains that he had heard Tapu Koko's voice, so he had took off after it, and when he found Tapu Koko, the ring had come floating down to him. Kiawe wonders how Tapu Koko had obtained the Z-Ring, but Ash says it simply felt like Tapu Koko had been telling him the ring was for him. Lillie explains to Ash that she has read about Tapu Koko, and that it is very well known as the guardian who likes to help travelers, but also likes to play tricks and can punish people if it thinks it is necessary. Upon hearing that on rare occasions, Tapu Koko can provide gifts to people, Mallow realizes that Tapu Koko must really like Ash. Sophocles checks with Kiawe who reveals that he got his Z-Crystal from clearing the Akala Island's grand trial. Ash becomes excited that he can now use Z-Moves just like Kiawe, but Kiawe objects strongly, telling Ash about the duties of Z-Move users. Ash says he doesn't understand what Kiawe said, but reassures Kiawe that he will do his best. Professor Kukui tells the class that Samson Oak will be their teacher for the next lesson. Later, Samson Oak, wearing an Exeggutor costume, teaches the class about the different appearances and types of the Pokémon in different regions as Sophocles comments on certain Pokémon's heights being totally different. Oak explains that the reason Exeggutor is different in Alola is because of the local climate. He then says that the Alolan Exeggutor they are looking at is a regional variant, and explains the biology of Exeggutor - they are usually Grass/Psychic. This surprises Lillie who mentions that in Alola, Exeggutor are Grass/Dragon. Ash is surprised about the typing of Alolan Exeggutor and runs forward to stroke its tail. Lillie tries to warn Ash about this, but he ends up getting thrown up a ladder before Lillie explains that the tail has a mind of its own.
At Professor Kukui's house, Kukui treats Ash and Pikachu to dinner, where both of them finish their food very quickly. Ash and Pikachu pet Rockruff, and Kukui explains that it has taken a liking to Ash. As Ash continues to pet Rockruff, Kukui receives a phone call from Mallow and agrees to proceed with a welcome party planned for Ash on the following day. The next morning, Ash and Pikachu are late to school, and rushing to make it on time. As they arrive, they are greeted with confetti and Popplio's bubbles, and Mallow explains that they had planned a surprise party for Ash. Sophocles and Togedemaru start by issuing a challenge to Ash and Pikachu, which Ash mistakes for a battle. However, he soon finds out that it is actually a balloon popping challenge. Sophocles uses Togedemaru's spikes to gain the lead, and Lillie tells Ash that he can also use moves to burst the balloons. Ash commands Pikachu to use Thunderbolt, but it is absorbed by Togedemaru's Lightning Rod Ability. She then uses Zing Zap to burst the remaining balloons, easily winning the challenge for Sophocles. Lana and Popplio then challenge Ash and Pikachu to a race, unknowingly being watched by a yellow Pokémon from afar. Although off to a strong start, Pikachu starts to fall behind, and Popplio eventually wins the challenge with its superior swimming speed.
Next, Ash is up against Kiawe in a Tauros race, with Kukui and Samson Oak watching them from the balcony. Oak asks the professor if he will take part in the party, to which Kukui replies that he is the fifth surprise. The race ends with Kiawe winning in a photo finish. Kukui walks up to Ash for his surprise, but Mallow says that it is time for lunch first. As they all eat, Ash hears a Pokémon's cry and Tapu Koko appears, much to everyone's surprise. Ash thanks it for bestowing him the Z-Ring, but Tapu Koko grabs Ash's hat and flies around with it. It then flies off towards the forest, with Ash on its heels.
Tapu Koko and Ash race to the forest and everyone else follows behind. In the middle of the forest, Tapu Koko returns Ash his hat, and reveals its will to battle him. Tapu Koko's Electric Surge comes into effect, and it lunges at Pikachu. Pikachu manages to dodge Tapu Koko's Dazzling Gleam and proceeds with Thunderbolt, but this has little effect. Tapu Koko charges at Ash and activates his Z-Ring. Ash realizes Tapu Koko wants him to use a Z-Move. Ash prepares to launch his first Z-Move, as everyone watches nervously. Ash and Pikachu make the required pose and Pikachu fires a strong Gigavolt Havoc, causing a huge explosion. However, Ash's Electrium Z shatters as the explosion settles, and Tapu Koko flies away. Mallow is impressed at how powerful Ash's first Z-Move was, but Kiawe notices that Ash's Z-Crystal had disintegrated. He explains that it was still too early for Ash to fully utilize Z-Moves, as he had not taken a trial. Upon hearing this, Ash decides to participate in the island challenge to prove his worthiness, and his classmates agree that they will be cheering for him.
Back at Kukui's house, Ash receives an Alola Pokédex from Professor Kukui while having dinner, as Ash looks forward to his island challenge.