Dan Kuso's life changed one day when cards fell out of the sky, which he and his friend Shun used to invent a game called Bakugan. With other friends, they form a group called the Bakugan Battle Brawlers, and then are accidentally dragged into fighting for the fate of Vestroia (the Bakugan's home dimension). Vestroia loses its natural balance and merges with the Earth and many other worlds. An evil Bakugan called Naga was tempted to take the power of the Infinity and Silent Cores, which formed the Perfect Core that balanced Vestroia, but absorbed too much negative energy and thus was trapped within the Silent Core and destabilised Vestroia. So Dan and the brawlers decided to bring back balance by meeting new friends and allies in the other worlds, learn more about the origin of the Bakugan; and facing Naga, a rogue bakugan who seeks the mighty Infinity Core so that he could complete the all-powerful Perfect Core and have almighty power and absolute control over Earth and Vestroia.