So here is a headcanon that popped up recently.
Zuko and katara are the reincarnations of the two lovers. Zuko being Oma, and Katara being Shu.
When Shu was killed, this brought great dread to Oma. She promised herself, that in the next life, Shu would be protected at all cost.
Suddenly time moves in a flash, and now they are born into new bodies, opposites of their last reincarnation. One born of fire, and the other of water.
Through this life, they find themselves at crossroads where they are sworn enemies, each soul always pleading for the other to Remember…
Shu tends to always find himself in danger, Oma being the one to save him.
One occasion involves pirates.
And another involves falling rocks.
Oma, is even able to help Shu release the pain he had been feeling since he was a child.
But the most significant event was when they partnered to face off Oma’s Crazed sister.
Oma could remember as the Lightning moved to hit its target, to strike Shu dead In his tracks.
Not again, not this time; he would not die this time.
Shu had died last time, and in the name of love.
So now it was Oma’s time to die for love..
So she leapt and caught the Lightning, absorbing it into her flesh.