With Professor Kukui down to his final Pokémon, the Island Guardian of Melemele Island, Tapu Koko, intervenes and requests to be Kukui's final Pokémon in order to battle Ash. Ash, with Naganadel and Pikachu remaining faces one of the toughest battles he has ever had. Will Ash manage to break through and defeat the Island Guardian?

Ash has made a decision to return to Kanto with a new goal of travelling more of the world to face stronger trainers. However, he has been struggling to tell everyone at the Pokémon school, but as he is trying to work out how to do it, Solgaleo appears in front of him. In addition to that, Team Rocket have received new orders to return to Kanto and Lillie & Gladion decide to go searching for their father. It is time to say goodbye.