You, a trainer from the Kanto region, had recently moved to the Alola Region. It was a pretty place with Pokémon you had pretty much never seen before, and ones you had seen before looked just a little different.
Listening in on the local chatter, you overhear that paying respects to the great Tapu Koko before starting on your journey was said to give good luck. You'd need all the help you could get with your luck, so, why not head up that way?
Up on your way to the Ruins of Conflict just after receiving your starter, you notice a blonde-haired girl who looked desperate for help looking towards you. On the bridge to the ruins, a unique-looking Pokémon was being attacked. The blonde haired-girl, Lillie, the daughter of the President of the Aether Foundation, spoke.
"Ah... never mind me... You have to help it! Please! Save Nebby!"