In the years fallowing Sozin’s Comet all of the members of the gang had drifted off to start new war free lives. Toph had gone home and worked things out with her parents. Sukki, Tylee and the other Kyoshi warriors had return to Kyoshi Island and for a while Sokka had joined them. However it was not long before he had to return to attend to his duties in the South Pole. Sukki had retired and joined Sokka not long after that. Zuko, who had of course become the Fire Lord, married Mai. Aang as Avatar had traveled the world with Katara by his side.
Katara had loved traveling with Aang but after a while she had grown tired of it and had decided to settle down somewhere and wait for him to finish sewing is wild oats. She knew he would, in time, return to her.
For a while she considered going home but had decided ageist it. It was cold there, and a long way for Aang to travel to see her. Many more places were considered before she decided on the Fire Nation. Zuko was there, they got along well, and she could work as an ambassador for the Southern Water Tribe.