On the other side of the world, there exists another mysterious, mirror-like dimension known as the Reverse World. In this unique space lives the legendary Pokemon Giratina, a god-like Pokemon who soon finds itself in a great struggle with the legendary Pokemon Dialga! Why are these two Pokemon fighting? And what is the secret of this Reverse World?

Meanwhile, Satoshi and his friends are traveling when they are greeted by yet another legendary Pokemon, Shaymin. This cute and somewhat cheeky Pokemon holds the secret to the battle between the two god Pokemon, but something unexpected happens to it during its journey. In order to save both worlds, Satoshi joins forces with it to stop the fighting once and for all!