Well in this story, a super volcano in a region is controlled by a powerful pokemon. The pokemon is stolen by Team Disaster so they can use it's power to wipe the region off the map, to show their power. The volcano is destablized when Team Disaster steal the pokemon controlling the super volcano, meaning the volcano will erupt. You are the son/daughter of a geologist that knows the volcano will explode and kill everyone in the region and possibly destroy the world. So you are set on a journey to try and recover the mysterious pokemon. The gym leaders will be Team Disaster elite, so every one you defeat you get one piece of the Volcano Slate, which can be used to free the mysterious pokemon and save the world.