The theme of friendship and mentorship also pops up a lot. Even though they are from different eras, they can still form a bond. Aang can act as a mentor to Korra, guiding her through spiritual challenges that he has already faced. And Korra can show Aang how the world has changed and how she is adapting to new threats in a different time.
One great aang and korra fanfiction is 'The Avatar's Bond'. It beautifully explores the relationship between Aang and Korra across different timelines. They face challenges together and learn from each other's experiences as Avatars.
Well, perhaps Korra could learn some of Aang's early airbending techniques. Since Aang was the first Avatar to master airbending in a long time, he might have some unique knowledge to share.
It could change the way benders view the Avatar's power. Seeing two Avatars from different times interact might make them realize the vast potential and flexibility of the Avatar spirit.
He could meet his future self. It would be an interesting encounter as he could learn from his future experiences and wisdom. Or he might meet people who have studied his past adventures and see himself through their eyes.
The 'lemon' aspect might be a bit hard to come by in a clean way as it often involves inappropriate content. But for normal Korra and Mako fanfictions, you could also try FanFiction.net. Some stories there might show their relationship developing, their adventures together, and how they support each other, which can be really interesting to read.
He might start by observing. Aang is a curious person, so he'd likely watch how people live, how they interact with technology. He may also try to find other benders to learn about any new developments in bending. And he'd probably use his kind heart to make friends easily in this new future environment.
Korra could meet the founders of the different bending disciplines. She could meet the first water benders and learn about the purest form of water bending. This would not only enhance her own skills but also give her a deeper connection to her water - bending heritage.
In some fanfiction, Aang's tattoos might be depicted as glowing with a special power when he reaches a new level of understanding or connection to the Avatar state.