Maybe he fell in love with her when they left to search for the man that killed her mother. Thinking back, Zuko decides that's probably it. He always knew that she felt deeply, and he had learned in the catacombs that her pain and anger were raw, completely at odds with her normal calm demeanor. Still, there was something different about those days.

She was cracks in a glacier, strong but fragile, and, he believes, achingly, painfully beautiful. She left a girl-a mature, motherly girl, but no more-and came back a woman. He respected her as an equal, perhaps as a better.

After that, it was very simple for her to become one of the most important people in his life. It had been so long since he had someone to fight at his back, and she fit, perfectly, and there was no need to ask. He would give his life for her, she was willing to kill for him-but she knew, when he didn't, that to kill his sister would be to kill some part of him as well. He didn't know how, but she knew.

For some reason, Zuko thought that they would just fall into place. He never questioned that assumption, never even considered it, it just snuck into the back of his mind and grew like vines, fed by the water of her blue-river eyes and refusing to be burned away. She smiled at him and held his hand as they sat in the palace, waiting for news, any news, and it was only a matter of time.

But then-then Mai was there, and time had given up. Of course, he thought, how stupid of him. Of course it was Mai, because Mai was easier. Katara was cracks in a glacier and roaring rip tides and still waters running deep, and Mai was the frozen pond that wouldn't melt below his feet. He could be with Mai, but he was no good with water. Aang was the one who had mastered waterbending, he was the one who could love Katara properly.

Of course.

Time passed.

She was still the most important person in his life.

Mai was The One, but Katara was Another One, another letter to be sent out because the South Pole was very far away, like Ba Sing Se or Kyoshi Island, the far corners of the Earth that they had all scattered to when they were no longer bound on a bison's back. Katara or Sokka or Aang or Toph or Suki, the only difference was the name at the top. Mai didn't know that Katara's letter was always a page and a half longer than the others, and if she had known, she wouldn't have cared.

There was nothing odd about that, he would have told her but contented in telling himself. Katara was smart, a natural born diplomat if one didn't hit her weak spots, and she was the daughter of a chief, a valuable ally. He wanted her advice and her insight, and that was why he felt the need to spill out his heart at every turn. That was all.

But time passes.