Dan Kuso's life changed one day when random cards fell out of the sky. He and his friend Shun invented a game called Bakugan with these. Together with his friends Runo, Marucho, Julie, Shun, and Alice, they form the Bakugan Battle Brawlers and its members are accidentally dragged into fighting for the fate of Vestroia (the Bakugan's home dimension) against the Doom Beings. The season is the story of a dimension called Vestroia which loses its natural balance and merges with the Earth and many other worlds. An evil Bakugan called Naga was tempted and decided to take the Silent Core, a huge dark violet-colored orb of negative energy that along with the positive energy of the Infinity Core, forms the Perfect Core that balances Vestroia. So Dan and his friends decided to bring back balance by meeting new friends and allies in the other worlds, learning more about the origin of the Bakugan, and facing Naga, a rouge bakugan who seeks the mighty Infinity Core so that he could complete the all-powerful Perfect Core and have almighty power over Earth and Vestroia.