On Ash's first day at Pokémon school, Professor Kukui and the other students host a surprise welcome party for him, which includes contests against the other students' Pokemon. Soon after, Tapu Koko battles Ash and Pikachu in order to test their ability to use the Z-Ring. Ash and Pikachu manage to unleash the Z-Move "Gigavolt Havoc", but the Z-Crystal shatters after Pikachu's immense release of power. In order to regain the power of Z-Moves, Ash decides to undergo the island challenge.