Ten years after the events of Pokémon Sun and Moon, two teenaged siblings from the Kalos region move to Melemele Island in the Alola region with their family. Both are eager to partake in and complete the famous Island Trials for the chance to challenge the fearsome Pokémon League, and they each set off on their journey, each one with a Pokémon from home in tow.
Very shortly after, wormholes similar to the ones the Ultra Beasts came from appear all over Alola, only this time, magical creatures calling themselves "ponies" emerge from them. The two siblings come across two of them and agree to keep them safe and help find the rest of her friends along their travels, all while evading forces who wish to use the ponies for their own power-hungry ways, as well as solving the mystery of their appearance.
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Playing Pokémon Sun/Moon (or watching/reading an entire play/walkthrough) is not a prerequisite for reading this story, though many references to the events of those games (among others) will be made.
Rated Teen for language and Pokémon violence.