I'm not sure specifically as it's a fan - made concept. But it might be a crossover where Naruto is somehow related to Ozai from Avatar: The Last Airbender in a fictional scenario. Maybe it involves Naruto having some of Ozai's characteristics or being in a situation related to the Avatar world.
Well, in this fanfiction, a really interesting plot twist could be that Ozai was actually trying to protect Naruto all along, but due to some misunderstandings and the complex politics of the combined universes, it seemed like he was a bad guy. This would completely change the way Naruto views his father - son relationship. Also, it could be that Naruto has the ability to combine his ninja jutsu with Ozai's fire - bending in a way that no one expected, and this new power is the key to saving both the Naruto world and the Avatar world from a greater threat.
Aang could be an ally. Despite the OC being Ozai's son, Aang, with his forgiving nature, might see the potential for good in the OC. He could help the OC to understand the importance of balance and peace.
One idea could be that the OC, as the son of Ozai, struggles with the dark legacy his father left. He could try to redeem his family name by using his firebending skills for good, like helping to rebuild the Fire Nation in a more just way.
In fanfiction, Ozai's actions towards Zuko can be extremely cruel. Ozai has often been depicted as an abusive father. He burned Zuko's face, which is a very traumatic event for Zuko. In fanfiction, this relationship might be explored further, showing Zuko's struggle to overcome the psychological and physical harm caused by his father.
If we look at 'azula and ozai lemon fanfiction' from a creative writing perspective, it might be an attempt to explore the power dynamics and psychological aspects of their relationship in a very extreme way. But this type of fanfiction can be off - putting to many fans who prefer to focus on the more positive aspects of the Avatar story, such as friendship, growth, and heroism. It's important to note that such content should be consumed with caution if at all.
It's not appropriate. The original Avatar: The Last Airbender series is aimed at a wide audience, including younger viewers. 'Lemon' fanfiction often contains adult - themed content. Katara and Ozai have a relationship in the show that is based on enmity and conflict. Turning this into a sexualized relationship in fanfiction is a misrepresentation of the characters and the story, and is not suitable for the general Avatar fan community.
One common theme is redemption. Many fanfictions explore the idea of Ozai seeking redemption for his actions towards Ursa and their family. Another theme is love lost and found. They often show the relationship that was once there between Ozai and Ursa and the possibility of it being rekindled. There's also the theme of family secrets, as their relationship was filled with many secrets that are often explored in fanfiction.
I'm not overly familiar with this specific fanfiction, but perhaps themes of forbidden love could be common. Given their relationship in the original context, it might be something that's explored. Another could be redemption, where their love might be a catalyst for one or both of them to change.
I'm not sure specifically about 'ozai and ursa love' fanfiction. You could try searching on popular fanfiction websites like Archive of Our Own. There might be some creative works there, but it also depends on how popular this particular pairing is among the fanfiction community.