Yes, there are likely fanfictions out there with this concept. The Naruto fandom is quite large and diverse, so many creative and unique ideas get explored in fan - made stories. However, the quality and content can vary greatly from one to another.
Well, it could be that Fem Naruto has to prove herself to Fem Kyuubi. Maybe there's a prophecy or something that says only by uniting with Kyuubi can Naruto save the village in a new and greater threat. So, Naruto embarks on a journey to understand Kyuubi better. Along the way, they have adventures, meet new characters. Kyuubi starts to respect Naruto for her tenacity and Naruto admires Kyuubi's power. Their relationship evolves and eventually leads to them becoming mates, which also brings about a new era of peace and understanding in the village.
One common theme is power and how the combined power of Naruto and the fem kyuubi is used. Another is acceptance, as Naruto has to accept the fem kyuubi as his mate and vice versa.
One idea could be that the fem Kyuubi starts to show her affection in small ways. For example, she might protect Naruto more fiercely during battles. She could also start leaving little signs of her presence around him, like a soft growl when danger is near that only he can hear. This would build an interesting dynamic as Naruto tries to figure out what these new behaviors mean.
For Fem Naruto, her character development could be centered around acceptance. Accepting her own power, accepting Kyuubi, and being accepted by the village. Her relationship with Fem Kyuubi would be a catalyst for this. She would become more confident and less afraid to show her true self. Fem Kyuubi's development would be about transformation. She was once a feared entity, but with Naruto, she would transform into a more loving and protective figure. This transformation would be gradual, through their shared experiences and the deepening of their bond.
In a 'naruto is fem kyuubi's mate' fanfiction, perhaps the story begins with Naruto being drawn to the Kyuubi's chakra in a way he doesn't understand at first. The fem Kyuubi, on the other hand, is intrigued by Naruto's determination and spirit. As the story progresses, they form a bond that goes beyond the normal host - tailed beast relationship. They might have to deal with the reactions of the villagers who are either afraid or in awe of this new development. And together, they embark on a journey to bring a new kind of peace to the ninja world, one that is based on the unity of their unique relationship.
One possible plotline could be the two characters starting as enemies or at least with a lot of misunderstandings. As the story progresses, they gradually come to understand and trust each other, and a romantic relationship begins to form.
One popular 'naruto fem kyuubi mate fanfiction' is 'The Kyuubi's Female Bond'. It has an interesting plot where the female Kyuubi forms a unique bond with Naruto. Another could be 'Fem Kyuubi's Mate in Konoha' which explores their relationship within the village setting.
One interesting plotline could be the exploration of their relationship in the face of Naruto's journey to become Hokage. The fem Kyuubi might support Naruto in his training and political challenges, adding a unique dynamic to the story.
There could be a fanfiction where Fem Naruto discovers a hidden side of Fem Kyuubi. Maybe Fem Kyuubi has some memories or powers that were locked away and Fem Naruto helps her unlock them. This could set off a chain of events that not only changes the relationship between them but also has a major impact on the entire ninja world as they face new threats and opportunities together.