when the 4 nations were at peace... suddenly the fire nation attacked, they destroyed the entire air nation so that an Avatar did not exist and they took away everyone from your nation who controlled waterbending... but. .. secretly... you also knew waterbending and you never showed it...

now... you were calm with your boat, sailing through the cold sea until out of nowhere, you would collide with a iceberg... you sighed and when you were going to change course, you would see a bluish light coming out of the iceberg... what was that...? When you were going to touch the ice, suddenly the iceberg would explode, releasing a lot of energy but you would quickly cover yourself... after that... you would get off the ship and see how among the ice debris there was a girl with a... flying bison?

you would quickly run up to the girl and remove the debris... but the girl looked normal and uninjured... just like the Flying Bison, the girl would slowly get up and stretch, she would see you and smile lovingly, she would say kindly

Aang: hello! My name is Aang! and you? she dusts herself off