One common theme is power acquisition. For example, a character getting the power of airbending and how they learn to control it. Another is the clash of cultures. Since Naruto has its own unique ninja culture and airbending comes from the Avatar world, there can be a lot of interesting interactions between the two. And sometimes, friendship is a big theme too, like how characters from both worlds form bonds while dealing with the new concept of airbending.
Yes, there are quite a few. You can start by looking on fanfiction websites like Archive of Our Own or FanFiction.net. Just search for 'airbending naruto fanfic' and you'll find a variety of stories, some might focus on a character who can airbend in the Naruto universe, while others could be more about crossovers with the concepts of airbending from Avatar: The Last Airbender and Naruto's world.
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.
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.
There could be a fanfiction where the kiss is a moment of impulse. Mako and Korra have been through a lot, and the emotions just build up until they can't hold it back anymore. This could then lead to a series of events where they have to deal with the consequences of this sudden display of affection, like how it affects their friendships with others in the group.
Yes, there are likely some popular ones. Often, these fanfictions gain popularity because they explore the relationship between Mako and Korra in a way that the original show might not have fully delved into. For example, some might focus on the emotional build - up to the kiss, which can be really engaging for fans who are invested in their relationship.
She could also get angry. Korra is a strong - willed character. After the shock wears off, she might lash out at Asami. She could yell and demand an explanation. She might feel that she has been wronged and wants Asami to know how much she has hurt her.
Archive of Our Own is a great place to start. It has a large collection of fanfictions, and you can easily filter out any inappropriate content. Just search for Korra and Mako, and you'll get a variety of stories exploring their relationship, from friendship to romance, all within the boundaries of a proper and respectful narrative.
The meeting could start with a sense of mystery. Itachi might appear out of nowhere in Korra's world. Korra, sensing his strange energy, would be on guard. Itachi would be sizing her up, taking in her appearance and the power he can sense within her. They might exchange a few words, with Itachi's soft - spoken nature contrasting with Korra's more direct way of speaking. As they start to interact more, they would begin to learn about each other's abilities and the worlds they come from.