The main goal of the game is to stop the Shadow Pokémon epidemic and free the Shadow Pokémon that have been captured and brainwashed. You are rewarded with the satisfaction of achieving these goals and a sense of accomplishment.
However, there are some in-game rewards for completing certain objectives:
* Completing the story unlocks the post-game content, which includes new areas to explore, stronger trainers to battle, and more Shadow Pokémon to rescue.
* You can also earn different types of currency throughout the game by participating in battles and competitions, which you can use to purchase items, upgrade your Pokémon's stats, and unlock new abilities.
Let me know if you'd like to know more about the post-game content or how to earn currency in Pokémon XD!