Main article: List of Bakugan Battle Brawlers characters
In a dimension of Vestroia, a Bakugan called Naga decides to absorb the energy of the two cores that keep the dimensions in place. He absorbed too much of a negative energy found in the Silent Core. The Infinity Core, the positive energy core, has been absorbed with Naga's sister, Wavern.
The story centers on group of friends who find metallic cards which have fallen from the sky. They name themselves the Bakugan Battle Brawlers and consist of eight children: Dan, Shun, Runo, Marucho, Julie, Alice, and later Masquerade and Joe. Together they learn more about the origin of Bakugan, the game involving them, and battle against Hal-G and Naga.