Ash Ketchum goes to school on Melemele Island with his classmates, Lana, Kiawe, Lillie, Mallow, and Sophocles. After being recognized by Tapu Koko, Ash accepts the island challenge into order to prove himself worthy of the power of Z-Moves.
After meeting an unidentified Pokémon Lillie names Nebby, discovering its origins, and fighting the Ultra Beast Nihilego, they join forces with the Aether Foundation to form the "Ultra Guardians", whose duty is to capture stray Ultra Beasts so they can be returned to their homeworlds.
