It could be an original character created by the fanfiction author. This character might be a descendant of the original Kyuubi, but with a female form and her own distinct personality.
The idea of Naruto and a female Kyuubi in fanfiction has a lot of potential. It can give a fresh take on the Naruto story. For example, in some fanfictions, the female Kyuubi might have a different backstory compared to the original Kyuubi. This can lead to new emotional arcs for Naruto as he gets to know her. Their relationship could start off as rocky, with Naruto being a bit wary of her, but as time goes on, they could grow to trust and rely on each other, creating a heartwarming story.
Obviously Naruto is a crucial character as he is the host of the Kyuubi. His family members like his father, Minato, and his mother, Kushina, are also important. Minato was the Fourth Hokage and had a role in sealing the Kyuubi within Naruto. Kushina was the previous Jinchuriki of the Kyuubi.
Their relationship could start with mutual understanding. Naruto, who has always had a connection to the Kyuubi, now with a female form, could start to see her as more than just the beast inside him. They could have conversations about his dreams and her past.
At first, Naruto might be a bit scared or hesitant. But as the female Kyuubi shows her care and concern for him, he would start to trust her. They would gradually develop a mother - son type of relationship. The female Kyuubi could be strict at times to make Naruto a better shinobi, but also very loving.
There could also be a romantic relationship in some fanfics. This would bring a whole new dynamic to the Naruto universe. It might start with small moments of mutual understanding and attraction, gradually evolving into a full - fledged love story. However, this would also face many challenges, like the differences in their nature (human vs. tailed beast) and the opinions of others in the ninja world.
Naruto, Hinata and female Kyuubi in fanfiction are important as they allow for a different exploration of the power structure in the Naruto world. Naruto has the power of the Nine - Tails, and a female Kyuubi could bring a different perspective to that power. Hinata, with her Byakugan, could interact with this new power dynamic in unique ways. It could also show how their relationships evolve not just on a personal level but also in terms of how they are perceived in the ninja community. For example, if the female Kyuubi is accepted, it could change the way Naruto and Hinata are viewed as well.
One well - written female Kyuubi character could be those who are portrayed as strong - willed. They don't just submit to Naruto but have their own ideas and goals. For example, a character who uses her powers to protect Naruto and the village in her own way, not just following Naruto blindly.
One well - written female Kyuubi character could be the one who is depicted as having a complex personality. For example, she might be fierce in battle but also show vulnerability when it comes to her relationship with Naruto. Another could be a female Kyuubi who has a strong sense of justice, despite her origin as a powerful and sometimes feared entity. This kind of character adds depth to the fanfiction.
You can start by looking on fanfiction websites such as Archive of Our Own (AO3). There are often specific tags for different pairings like 'female Naruto' and 'female Kyuubi'. Many authors explore this unique pairing there, and you can filter the results to find exactly what you're interested in.