Bakugan Battle Brawlers begins with Danma Kuusou, a boy who invented the game Bakugan with his friend Shun Kazami after mysterious and seemingly random cards fell out of the sky. Together with their other friends, they form a team called the "Bakugan Battle Brawlers" in order to play this new game together. But unknown to these young friends, Bakugan is much more than a simple past time. Their game accidently sucks them into an alternate dimension called Vestroia, the home ground of Bakugan.
Vestroia has recently come under attack by creatures known as the Doom Beings. This realm is balanced by the Perfect Core, which itself is formed by the Infinity and Silent Cores. When the evil Bakugan Naga attempted to take this great power for himself, he was unable to absorb the negative energy he wished to steal and found himself trapped in the Silent Core. Now, his presence within the core has destabilized Vestroia and attempts to merge with Earth as well as many other worlds. Danma and his friends must team up with individuals from other worlds who have also been drawn into this epic battle. As Naga is seeking the Infinity Core so that he may complete the Perfect Core in order to gain control of Vestroia, Earth, and all other worlds, time is of the essence in this devastating war of worlds.