She leaves with the Avatar.
Of course she does. Because Aang is the hero, the leading man (even if he is only twelve), the one who gets the girl. And Katara is his leading lady: the one who found him, who supported him, believed in him, healed him. She is his first teacher. His first kiss. His first love. It is clichéd (she is the first girl he ever met), but it is also, clearly, meant to be. They make one another stronger; together they can change the world. And whatever Zuko might think he felt in those minutes after the lighting, thinks he might feel now, it is nothing compared to the bond the Avatar and his water bender share.
It is only infatuation. Gratitude. Curiosity. She has always intrigued him, from that first moment in the South Pole when she'd whisked the Avatar away from his outstretched hand. She is spirited and talented. She is kind – even to him who least deserves it.
But that is all it is. Kindness. Fascination. And he is not so selfish as to ruin everything just for that.
The world needs the Avatar. And the Avatar needs Katara.
Zuko only wants her.
And he has Mai, who loves him, and came after him, and accepts him (for the most part) just as he is. Mai needs him. And the Fire Nation needs Mai – or someone like her. A strong woman to stand beside their new Fire Lord and bear strong, fire bending heirs. Someone who knows their culture and their politics.
Katara is strong, but she is not Fire Nation. They should never have been a part of one another's world. So even though she is beautiful, and strong, and perfectly imperfect. Even though she challenges him, and supports him, and makes him laugh. Even though he wants her so desperately it almost feels like he needs her (but he doesn't, he can't), he does not say a word as she follows her destiny up onto Appa's saddle, and he stays with his on the ground.
It's just as well that her destiny lies elsewhere. They are fire and water, sun and moon; they are not meant to coexist.
And she is so young. Really, still a child. And he is not. And the things he thinks (fears) he might feel for her –the things he wants– aren't right. Not now.
Maybe not ever.
When she shows up on his doorstep, a few years later, she is no longer a child. Katara is a woman, come into her own. She is still spirited and talented and kind. Still beautiful and strong and perfectly imperfect.
She is also alone.
At first he thinks she is here because she does not know where else to go. The South Pole is full of memories of him – finding him, training him. And the North is full of old traditions that would chain a free spirit like Katara. She has friends in the Earth Kingdom, but the Earth Kingdom is crowded and noisy and dry. The Fire Nation (in his palace, if nowhere else) is quiet and calm; there is water here, from the ponds in his gardens to the ocean licking along the shores of the island nation. Perhaps it is just enough like home to soothe her spirit.
And, perhaps, she needs a friend –the only one who doesn't judge, who has no right to judge– now, when the love of her life has abandoned her for the sake of the world.
He is alone as well. Mai has long since parted ways with him. He was not surprised. (He also was not sorry.) And, despite the urgings of everyone around him, he has taken an interest in no others.
How can he when his heart still yearns for another?
His advisors worry that he will never have an heir. Zuko thinks perhaps it is better to let his bloodline die. That perhaps it is Agni's will. It is a line tainted with a craving for power, with destruction, with hate. He does not say this to anyone. Not them. Not her.
His advisors would worry. Katara would scold him.
He joins her in the garden after another long, draining, council meeting. He stands beside her in silence as they watch the turtle ducks in the pond. She rocks them gently on waves of her own making and laughs. The sound tickles his ears like tinkling bells, and warms his heart in ways that make him think there is more than intrigue and gratitude –more than infatuation– dwelling for her there.
The laughter fades, but not the sparkle in her eyes, and something inside him clenches – almost painfully tight.
Yes, far more than infatuation. And he can admit now what he could not then: he loves her. Perhaps he always has. And looking at her he wonders how anyone could not. How Aang could have let her go – even for the world.
She should be heartbroken, but she is not. And he thinks this is a testament to her resilience and her strength of will. He is glad that his home can be a refuge for her. Glad he's never told her about the lingering, treacherous, things his heart and body want from her. And he thinks that he can keep these feelings hidden away for as long as she needs him to.
And then she turns to him, and her hand touches his forearm gently. He sucks in a sharp breath and curses himself for the telltale sound. But when he meets her gaze she is smiling and there is something in her eyes that says perhaps she feels the same way he does – perhaps she always has, even all those years ago, but she has not been able to act on it until now.
His eyes speak with hers, a silent question, and her smile widens as she nods, an infinitesimal dip of the head. And then she is in his arms and his lips are brushing hers ever so hesitantly, and then less hesitantly as she responds, lips curving subtly under his. And her fingers are on his neck, curling in the soft hairs at his nape, and his are digging into the gentle curve of her waist, and it's exactly what he wants. What he needs.
Because Zuko needs her. He needs her kindness, and her spirit, and her strength.
And somehow, miraculously, Katara needs him.
They are fire and water. Sun and Moon. But they are also yin and yang. Balance and harmony. Energy and respite. They are two halves of one whole. They always have been.
And the things that he wants are no longer wrong, they are right.
Perhaps they always were.
She stays with the Fire Lord. Of course she does. Because they make one another stronger. And together, they can change the world.