They could encounter past Avatars and learn unique bending techniques from them. Maybe they'll find ancient Air Nomad artifacts that hold special powers.
They could meet past Air Nomads. These could be great benders or spiritual leaders who can offer wisdom and advice.
In this fanfiction, they might discover long - lost Air Nomad artifacts at the Southern Air Temple. These artifacts could hold the key to new airbending techniques.
The main characters are surely the members of the gaang, which include Aang, Katara, Sokka, and maybe Toph. Aang is the most important as he is an Air Nomad and the Southern Air Temple is his heritage.
She might have a lot of adventures. For example, she could encounter powerful Uchiha ninjas and learn their unique jutsu. Maybe she'll get involved in some sort of mystery within the kingdom, like a secret about the Uchiha's power source. Also, she could form unexpected friendships or rivalries with the Uchiha clansmen.
They might have an adventure where they stumble upon a hidden magical grove. In this grove, there are plants with unique magical properties that they've never seen before. They could spend time studying these plants and perhaps even discover a new potion ingredient.
Another possibility is that he gets involved in the early days of the Akatsuki. He might try to change the course of the organization, perhaps by convincing some of its members to abandon their more evil plans. Since he's already a retired and experienced ninja, he has a different perspective on things compared to when he was younger.
Goten could meet the younger versions of his friends like Krillin or Yamcha. They might be a bit skeptical of him at first. He could also run into Master Roshi, who would probably be interested in Goten's abilities and might try to teach him some old - school techniques. And there's a chance he meets Bulma, who could be intrigued by his futuristic knowledge and might even try to get some tech ideas from him.
Naruto would meet his younger self. This would be a really strange situation. He could also meet all the important shinobi from the past. For example, the First and Second Hokage. He might have a chance to learn from them directly, instead of just hearing about them in stories. Additionally, he could meet some of the characters who were only mentioned in passing in the original story but had a big influence in the past.
Well, in this fanfiction's training trip, Naruto may come across different clans with their own exclusive fighting styles. He could engage in friendly sparring matches with their members, which would not only enhance his combat abilities but also his understanding of different cultures within the ninja world. He might also find some ancient artifacts that hold great power and have to figure out how to use them properly without being corrupted by their power.
Obviously, the main characters would be the Gaang, which includes Aang, Katara, Sokka, Toph, and Zuko himself since he's the one being kidnapped.