After seeing the power of Z-Moves while encountering Ash at the Pokémon School, Team Rocket decides to hunt for their own Z-Crystals so that they can keep level with Ash. In doing so, they encounter the Team Skull grunts who have been causing trouble on Melemele Island. In addition to that, while hunting for the stone, they discover the Totem Pokémon, Raticate. Will they find what they are looking for?

While at the schoo, Ash learns of a powerful trainer who has come to Melemele Island. Ash eagerly finds this trainer and challenges him to a battle. The battle is strong with the trainer's Z Move coming into full force but soon after the battle starts, Lillie appears and confirms that this trainer is her brother, Gladion. Why is Gladion here?