Pokemon: Giratina & the Sky Warrior! (manga)

Shaymin is a peaceful Gratitude Pokémon, lives happily in forests and fields of flowers. But one day Shaymin is accidentally drawn into a battle between the Legendary Pokémon Giratina and Dialga. Whisked away far from home, Shaymin is found by Ash, Dawn and Brock, who soon discover that this new Pokémon is full of surprises! Of course Team Rocket wants to get their hands on Shaymin, and so does a mysterious man named Zero. Even Giratina is in hot pursuit of this little Pokémon--and just what do Giratina and Shaymin have to do with the dimension known as the Reverse World?