In the legendary past, before the creation of Poké Balls, an Aura-guiding Pokémon called Lucario senses two rival armies about to clash near Cameran Palace in the Kanto region. He telepathically informs his master, Sir Aaron, through a nearby crystal just before being attacked by three Houndoom. During the battle, Lucario is temporarily blinded, but is still able to use his Aura Sphere to defeat the Houndoom – sensing their movements with his Aura abilities.
The Queen of Cameran, Lady Rin, decides it is right to die with her people, so Aaron leaves on his Pidgeot to meet up with Lucario, but is attacked by a rival group of Skarmory on the way. Aaron tells Lucario that he is leaving and will not be coming back, and when Lucario tries to go with him, he is automatically sealed in Aaron’s staff. Pidgeot returns to the queen with only Sir Aaron’s staff, and the queen realizes that Sir Aaron must have sacrificed himself by using his own Aura to stop the war. Since then, he was revered as a hero, and only his staff remained for his legacy.
Many years later, Ash, Pikachu, Brock, May and Max arrive at Cameran Palace to celebrate the life of Sir Aaron. Ash competes in a Pokémon battle tournament, and wins against a Trainer named Kidd Summers and her Weavile. That night, there is a royal ball, and as the winner of the tournament, Ash is rewarded with the title of “Hero of the Year” and the privilege to hold Sir Aaron’s staff. Team Rocket join the dance too, but Meowth runs off to follow Kidd, who reveals herself as an agent, performing research on Mew, which is known to appear at the palace.
Ash and May’s Pokémon run off into the attic of the palace to play. However, Kidd’s two Weavile attack when Mew joins in. Mew teleports away with Pikachu and Meowth, and Max finds out what has happened. In the ballroom, Ash watches the fireworks display, unaware of what is happening to the Pokémon. Suddenly, Lucario is freed from the staff after one thousand years due to Ash’s Aura having a close resemblance to Sir Aaron’s. Lucario is very confused about what has happened since the time he was sealed, and goes to search for answers.