Her personality might become more innocent. As a Kyuubi, she was powerful and perhaps a bit menacing. But as a little girl, she could be curious about the world around her, constantly asking questions. She might also be more vulnerable and seek protection from those she trusts.
A common theme is identity crisis. Sasuke suddenly being a girl would make him/her question who they are now. Another theme could be acceptance, both from Sasuke herself and from the other characters. Also, there might be a theme of newfound friendship. As a girl, Sasuke might make new friends that he wouldn't have made before.
One storyline could be that Naruto, now a girl, tries to keep her identity a secret while still being a ninja. This would add an extra layer of intrigue to her missions. Another could be that she has to deal with romantic interests in a new way. Maybe some characters who were just friends before start to see her differently.
In such a fanfiction, the plot could involve Naruto's transformation causing chaos in the village at first. People who knew Naruto as a boy are now confused. But Naruto (as a girl) is determined to show that she's still the same person inside. She might start wearing different clothes that are more feminine but still keep her ninja gear. Her sensei, like Kakashi, would have to adjust to training a female Naruto, and there could be some humorous moments in their training sessions as Kakashi tries to be more sensitive to her new situation.
One common theme could be the idea of innocence. Since kyuubi is depicted as a little girl, there might be themes of her pure-heartedness and naivete in a world that may be complex or dangerous. Another theme could be growth, as she might be shown learning about the world around her and evolving as a character.
Well, one possibility is that Naruto, now as a girl, might face new challenges in the ninja world. People could underestimate her at first, but she would soon prove them wrong with her skills. Maybe she would also develop new relationships. For example, her friendships with Sasuke and Sakura could change in interesting ways. She might have to deal with different expectations from her peers and sensei.
Well, often in such fanfiction, the change might lead to new relationship dynamics. Sasuke as a girl could have different interactions with Naruto, for example. Maybe there would be more emotional and less combative exchanges at first. The story could explore how Sasuke deals with this new form and the reactions of other characters in the Naruto universe like Sakura, who might be jealous or more protective.
I haven't heard of a fanfiction where Kyuubi turns Naruto into a futa. Naruto fanfiction often focuses on things like character development, new adventures, or different power - up scenarios. This concept is rather unorthodox and might not be as common as more mainstream fanfiction ideas. It's possible that it exists in some corner of the vast fanfiction universe, but it would take some serious searching to find it.
Well, without having a particular 'kyuubi is a little girl fanfiction' in mind, you could also check out fanfiction.net. Sometimes, the best way to find such a story is to use relevant keywords in the search bar and then browse through the results to see if there's one that catches your interest. Keep in mind that different authors may have different interpretations of the idea.
One possible plot could be that the little - girl - Kyuubi is found by the main character. The main character, at first, is confused but then decides to take care of her. As she grows up in this new form, she starts to learn about human emotions and relationships, all while having some of her Kyuubi powers hidden within her, which she gradually discovers and has to control.