Pokémon Eevee Tales!

Back in time 30 years ago, when the Island Trial Challenges were booming in the tropical Alola, the only way to become the Island Champion was to claim all 18 Type Z-Crystals but the final crystal that could be obtained suddenly stopped appearing in Alola. There was a team of 8 trainers who had gathered the other 17 Crystals: Polly, Jane, Ishaan, Chad, Braiden, Rea, Linnea and Sakura. All 8 are on even ground, whoever could find the missing Z-Crystal would be named the strongest trainer in Alola.
Now, the search has died down, and most trail goes had given up until a new group of trainers emerged who were going to reignite the flames of competition. Who will become the next Island Challenge Champion?