Another theme is the way she is perceived in the ninja world. As a girl, she may face different expectations and prejudices. Some fanfictions explore how she overcomes these and still manages to be a strong ninja. In many of these stories, she has to prove herself more because of her gender.
Love and romance are also quite common. The idea of girl Naruto having romantic feelings for Sasuke or vice versa is explored in many fanfictions. It can be a slow - burn romance or a more immediate attraction, adding a new dimension to their relationship.
One possible plot could be that Sasuke uses some kind of rare jutsu accidentally while sparring with Naruto. This jutsu has the side effect of changing Naruto's gender. At first, Naruto is shocked and confused. But then, he (now she) starts to discover new aspects of the ninja world as a girl. For example, she might notice how differently she is treated by some of the male ninja. And Sasuke, feeling guilty, tries to find a way to reverse the effect while also protecting Naruto from any potential harm that could come from this new form.
Maybe Naruto was trying to protect Sasuke from a certain danger. There could be a curse or a powerful enemy that targets male shinobi. So, Naruto uses a risky jutsu to transform Sasuke into a girl to keep him safe. Or it could be that Naruto found a strange ancient scroll with a transformation technique that he thought was something else and when he used it on Sasuke, it turned him into a girl.
Sasuke could also have a complex mix of emotions. On one hand, he has a long - standing relationship with 'Naruto' as a male friend. Now that he knows Naruto is a girl, he might start to feel a different kind of connection. He may become more protective, but also a bit confused about his own feelings towards this new - found knowledge. He might even feel a bit betrayed that Naruto has hidden this fact for so long.
Another plot could be that Naruto, as a girl, is underestimated by many in the village at first. But Sasuke sees her potential early on. This leads to a special bond between them where Sasuke becomes her protector and mentor in some ways, and Naruto tries hard to prove herself worthy of his attention and respect. They might go on missions together where Naruto's femininity adds a new dynamic to their teamwork.
Themes in 'naruto x sasuke turned girl fanfiction' can also include the alteration of power dynamics. Usually, Sasuke is a very powerful male character. But as a girl, the way she wields her power and how others perceive it can change. It might lead to situations where Naruto has to be more protective, or where female Sasuke has to prove herself more in a male - dominated ninja world. And of course, there's always the underlying theme of how their bond, which was so central in the original series, evolves in this new, gender - flipped context.
Sasuke might be initially shocked. He has always seen Naruto as a rival and suddenly finding out Naruto is a girl could completely change his perception. He may start to view Naruto in a more protective way, as his traditional views of gender roles might make him feel the need to safeguard her now that he knows she's female.
She could also change in how she approaches relationships. Before, as a boy, Sasuke was more reserved in his interactions with others, especially with Naruto. But as a girl, she might be more forward in expressing her feelings towards Naruto, whether it's friendship or something more. This could lead to some really interesting character development arcs and new plot directions in the fanfiction.