Drago returns to Earth with a new ally named Mira. The five original Bakugan that helped restore order to New Vestroia have been captured, Drago is now being targeted, and a group of humans known as the Vexos are taking over New Vestroia. With the help of Dan and the Battle Brawlers though, Drago believes he will have enough power to not only free New Vestroia but his friends as well.

Source: ANN

Note: This is a rare example where the sequel to the first series was premiered in North America almost a year (12.04.2009) prior to its broadcast in Japan (02.03.2010).

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Prequel: Bakugan Battle Brawlers
Sequel: Bakugan Battle Brawlers: Gundalian Invaders