AN:
This story is T and not M because there's no smut. There's lots of sex, but there's no depiction of it. I assume that's okay for T. It discusses adult topics but there is no serious violence depicted in the story.
Basic Info for this Universe (Can skip if you want to learn as you go.)
It's post war; ignore the Search and the Promise. The Prologue is 2 years after the war ended and the First Chapter is 6 months after that. I don't think anything from the canon will be taken out, but new information will be added to it.
Aang and Katara dated on and off for almost a year and a half total. Toph is working for the police in Ba Sing Se. Zuko and Mai got married after the Prologue but before the First Chapter. Ty Lee joined the Kyoshi Warriors and they are all on Kyoshi Island. Sokka is with Suki. Azula was in the asylum for the first six months after the war. She spent the next six months working on regaining the trust of her brother, Mai and Ty Lee (who visits periodically) and a year after the war, she was deemed free to do as she pleased (absent starting a rebellion).
Prologue
"Are you sure you want to do this?"
"Are you trying to get out of having sex with me? This must be a first."
"Of course I want sex, but I want you to want it. I don't want you to feel obligated."
"Well this is our wedding night, so it is an obligation in a way, but this is not repayment for you helping me out."
"Good because when I said there were no strings attached, I meant it. You don't owe me anything for this."
"I know and that's why I said yes. So let's go to bed."
"Maybe we should sober up first, and then see if you still want to."
Katara leaned forward, pressing her lips to her new spouse. "I want this. So turn out the lights and let's go."
"Yes, Ma'am."
"Don't call me ma'am."
"Yes, Mistress."
"Mistress Katara, I can get used to that."
"We already have nicknames. HOT!"
"You're such a goon."
"But I'm your goon."
"That you are. So stop it with the lip service and get naked."
"Ooh! A bossy mistress, how can I refuse?"
The clothes came off. Katara was expecting her first time to be rushed, as they were both drunk and horny, but to her pleasant surprise, it was nice and slow. If she had known better, she would have said romantic: soft candlelight, tender kisses and gentle nips of flesh as fingertips roamed across each other's bodies. This was a night of firsts as they went from kissing to sex, slowly exploring everything in between. This all sounds romantic, but they were NOT in love.
If you had told her a year ago she would have married the biggest womanizer in the Fire Nation (and possibly the world), she would have said you were crazy, but here she is, in the arms of one who is infamous for notches on the belt and being anti-marriage and anti-children, a certified true player for life.
This marriage would not change anything. Katara still had her freedom and her new spouse would still be a womanizer. No one would know of the marriage until the time was right, so they could continue on as if they weren't even dating, because they had never dated before.