500 years ago, Sir Aaron saved the kingdom of Rota when two opposing armies nearly destoyed it in a war. Now, a festival is held every year in honor of Sir Aaron’s deed. After winning a tournament competition, Ash is selected to be this year’s Aura Guardian. When a mysterious woman by the name of Kidd tracks down Mew, Mew disappears and takes an injured Pikachu and Meowth to the Tree of Beginning. At the same time, Lucario is set free from the staff Ash holds, mistaking Ash for Aaron. Lucario reveals that Aaron was no hero and abandoned the queen, along with trapping him in the staff. Now, Ash must rely on Lucario’s help if he’s to make it to the Tree of Beginning and find Pikachu. Kidd tags along too, only wanting to learn Mew’s connection to the tree. However, their adventure will cause more damage than intended, and the truth of the events of 500 years ago will finally be revealed!