Two teenaged siblings, having moved to the Alola region from Kalos, set off to complete the famous Island Trials, only for wormholes to appear across the region once again, this time summoning creatures from a mystical world calling themselves ponies
Twilight didn't get her letter to Princess Celestia on time and has been kicked out of school. Obviously she is angry and while she is angry that her friends never took her seriously, it is the one who kicked her out she wishes to exact revenge on.