Anon asked: Zucest + scars
When they were little, every time Azula got hurt, Zuko would kiss it better, so she ended up liking when those little wounds left a scar.
Zuko was extremely self-conscious when they saw each other for the first time after his banishment, because Azula had never really seen his scar. She thought it suited him very well. But she did resent that their father left a permanent mark on him while she had not, and that was part of the reason why she left those scars on his face during their fight on the ship. She knew it they'd heal, but it was still something. Zuko kept touching the spot over and over, even after the scars were gone.
After their Agni Kai, Azula felt a mix of pride and guilt over finally marking her brother. Zuko couldn't understand why he didn't resent her for hurting him like he resented Ozai. He kept touching it, and he'd focus almost exclusively on that when he looked in the mirror. Once they finally got together, they'd constantly leave small burns on each other's skin during sex, and Azula would kiss both of his scars and constantly leave Zuko's back all bloody. After they get engaged, Azula asks him to burn her above the heart like she did with him. Zuko would hesitate at first, but then give in. He would only truly relax after it was done and Azula didn't show any sign of regret (quite the opposite)