/An Understanding/
Aang never understood- not really- why Katara had left him for Zuko. He knew that Zuko was a great man, a powerful bender, and a loyal friend. Aang trusted Zuko with everything he had and believed he would be a great Firelord. Aang knew that Zuko occasionally had anger issues, but held no doubt that he could overcome his problems. Most importantly, Aang loved Zuko, the same way he loved Sokka, and all of his other friends. So maybe there was a part of him that could see the appeal of Zuko, but compared to him! He was the freaking Avatar and Katara should have been with him.
Not only did Aang not understand why Katara had left him; he also didn't understand why in hell! she would want to be with Zuko! The two of them were complete opposites, fire and water didn't mix peacefully. When he would see them over the years, they were constantly bickering and yelling at each other. For a long time, for ten long years, until the Avatar turned twenty-five he would not understand why the beautiful waterbender chose a chaotic love over a peaceful and steady love.
And then he and Toph slept together.
It was the third night they were all reunited in the fire nation to celebrate the second child between Zuko and Katara. While Aang no longer held the bitterness and apathy that he had clung so tightly to after the breakup- and he would be hard pressed to admit it- but Aang felt lonely. He missed being with someone, being in love. And a part of him said that he would always be in love with Katara, the part that made him lonely would repeat that over and over, and he would hope and wish and pray that she would return to him. But…there was another part of him, a part that was getting stronger, a part that kept saying it was time to move on.
And so, the battle between those two parts of him raged on. And he and Toph argued that night about how pathetic he was being. Aang was so angry. Toph was so angry. The fighting must have woken up half of the city. And then, blinded by anger, by fury, and by something else that had become so familiar it had been ignored, they kissed. Not a peck, not a gentle exploration, but a mean, passionate, and down-right sexy as hell, kiss.
And that was when Aang finally understood why Katara left him for Zuko. He understood what the pull had been, and understood now what he didn't back then. Opposites were a powerful thing and a passionate one, and he realized belatedly that what he and Katara had was never passionate. It was friendly and always filled with love, but it didn't make his skin sizzle, it hadn't caused either of them to want to have sex. Katara knew though; she saw what was there and what wasn't. For the rest of his life, Aang thought as he held Toph in her sleep, he would be grateful that Katara had understood very early on, that there would never be the right kind of passion between them.
Aang had never felt so strongly or had been aroused so thoroughly than when he was with Toph. There was energy between them, the love and hate, the peace and chaos, the air and earth, they were opposites. IT was magnificent, it was right. And Aang finally understood that.