One idea could be that Sasuke first discovers Naruto is a girl during a mission. Maybe Naruto gets injured and Sasuke has to tend to the wound, and that's when he realizes. This could lead to a whole new dynamic in their relationship, with Sasuke seeing Naruto in a different light and having to re - evaluate his feelings for this person he thought was a boy all along.
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.
One plot idea could be Sasuke as a girl trying to break gender barriers in the ninja world. She might face discrimination at first but prove herself through her skills. Another could be a love triangle where she is caught between Naruto and another character in a different way than in the original story because of her being female. Also, she could form an all - girl ninja team and lead them to great achievements, showing that girls can be just as strong as boys in the ninja arts.
First, understand the characters well. Know Sasuke's personality, his backstory, his goals. For the 'best friend' and the 'girl' characters, create distinct personalities too. Then, build a believable plot. Maybe start with small, innocent interactions between Sasuke and the girl that gradually lead to more complex feelings. Also, show the internal conflict in Sasuke about his feelings and his loyalty to his friend.
One thing that might make a 'Best Friend's Girl Sasuke Fanfic' special is the complex relationships it can explore. It could delve into the moral dilemma of having feelings for your best friend's girl, in the context of the Sasuke universe. Maybe Sasuke's character traits, like his brooding nature and his own complex relationships, add an extra layer of intrigue to this forbidden - love - type situation.
It could also have an impact on the overall plot. For example, other characters' reactions to Naruto being a girl could be explored. Some might be accepting, while others might be shocked or even hostile. This could create new conflicts and alliances within the fanfic. Additionally, Naruto's own journey might change as she now has to deal with Sasuke knowing her secret and how that affects her standing in the ninja world.
One possible plot twist could be that Sasuke, as a girl, has a different approach to her ninja skills. Maybe she focuses more on stealth and misdirection rather than brute force like she did before. This could lead to new and interesting battle scenarios where she outsmarts her opponents in unexpected ways.
In such a fanfic, Sasuke's character development could take a whole new turn. Instead of the typical brooding male persona, as a girl, she could show more vulnerability. Her relationships with other characters like Naruto might change. Naruto could be more protective of her, and Sasuke might have to deal with Naruto's over - protectiveness in a new way. Also, her goals as a ninja could be influenced by her secret, like wanting to prove that girls can be just as strong as boys in the ninja world.
Yes, there might be such fanfics out there. In the Naruto fandom, with a large number of fans creating various types of stories, it's possible that some would write a story where Naruto destroys Sasuke in a way that could be seen as Sasuke - bashing. However, these kinds of fanfics may not be in line with the overall spirit of the original work which focuses on their complex relationship and growth.