Following her standing up to Tapu Fini, Hapu has finally become the Island Kahuna of Poni Island. As he's there on the island to find the Kahuna, Ash challenges her to her Grand Trial. Her trial requires Ash to battle her with just one Pokémon. With Hapu using her Mudsdale, Ash faces a tough battle. Will he be able to win the Grand Trial and finish his research project?

Some mysterious Pokémon have arrived in Alola, and these mysterious creatures eat metal! They start causing havoc across Alola by eating the tools at the Pokémon School, and even James' bottle cap collection. James is angered and decides to chase down the Pokémon to get his revenge. Just what are they?