This is the 1st episode in the first season of Born to the Blade, an 11-episode serial from Serial Box. This episode written by Michael R. Underwood. 

For centuries the Warders' Circle on the neutral islands of Twaa-Fei has given the countries of the sky a way to avoid war, settling their disputes through formal, magical duels. But the Circle's ability to maintain peace is fading: the Mertikan Empire is preparing for conquest and the trade nation of Quloo is sinking, stripped of the aerstone that keeps both ships and island a-sky. When upstart Kris Denn tries to win their island a seat in the Warder’s Circle and colonial subject Oda no Michiko discovers that her conquered nation's past is not what she's been told, they upset the balance of power. The storm they bring will bind all the peoples of the sky together…or tear them apart.