X was a Pokémon Trainer child prodigy. But now he's depressed and hides in his room avoiding everyone--including his best friend Y. An attack on their hometown by Legendary Pokémon Xerneas and Yveltal, led by Team Flare, forces X outside... Now what?

Team Flare uses mind control to force the Vaniville townspeople to transport a huge tree containing Legendary Pokémon Xerneas to help them complete their ultimate weapon! Can X and his friends stop them and rescue Y's mother from their clutches...? Luckily Trainers Gurkinn, Korrina and Diantha arrive to help--each with a Mega-Evolving Pokémon!

Who will be the latest addition to X's Pokémon team...?