The Legend of Korra Episode 1.02 A Leaf in the Wind

Korra is living with her airbending teacher Tenzin on Air Temple Island. Frustrated with her inability to master airbending, she turns her attentions to Republic City's famous Pro-bending Arena, despite Tenzin's disapproval of the sport. She sneaks off the island and befriends two brothers, Mako and Bolin, who compete in professional bending matches as part of the Fire Ferret team. Korra is immediately drawn to Pro-bending's dynamic fighting style and joins Mako and Bolin's team when their waterbender teammate fails to appear. Korra has trouble at first when she discovers that Pro-bending is nothing like the sparring matches she is used to. However, she begins to instinctively use airbending techniques to dodge her opponents' attacks, winning the match. Tenzin, who witnesses Korra's performance, reluctantly allows Korra to continue Pro-bending and join the Fire Ferrets permanently.