Having arrived at another island in the Decolora Archipelago, Satoshi and his friends join Pansy as she heads to the top of its mountain to observe the beautiful Woodate Comet, which can only be seen once every 10 years. When the comet passes, it's said that Pokémon gather on this mountain and partake in a certain strange ritual. As the group reaches the top of the mountain, they discover the ruins of a battlefield where Woodate, revered as the hero of the island, used to engage in battle. As they head into its dimly lit interior, the Rocket Gang sneaks forth from the darkness, still gunning for Pikachu, but...!?