Now that Ash has decided to become a Pokémon School student in the Alola region, his classmates throw him a welcome party! Three of them challenge him to various competitions—a balloon-popping contest versus Sophocles and his Togedemaru, a land-and-water race between Pikachu and Lana’s Popplio, and a Tauros race against Kiawe. Finally, Professor Kukui challenges him to a Pokémon battle, but Tapu Koko interrupts. It wants to battle Ash instead—and it wants him to try out his very first Z-Move, Gigavolt Havoc! As Pikachu unleashes an astonishingly powerful burst of electricity, Ash’s Z-Crystal shatters. He decides to undergo an island challenge trial to earn a new one! (Source: Bulbapedia)