Well, it's a really cool manga actually! It's about a guy who wants to find a long lost friend. But to do so, he needs to be stronger. Thus he embarks on a Pokémon-Journey while having a small crystal known as a "Burst Heart" with him. A Burst Heart allows whoever has it to merge with the Pokémon inside the Burst Heart. For example, the main character's Burst Heart has Zekrom in it, thus the main character can fuse with Zekrom and obtain some of its powers.