In this kind of fanfiction, Naruto's training would take a whole new turn. Instead of just trying to control the Nine - Tailed Fox's chakra, he would be learning to be the Nine - Tailed Fox. He might have to adapt to new instincts and ways of thinking, which would be a great challenge for him but also a chance for character growth.
One possible scenario in this fanfiction could be that Naruto's transformation into a fox gives him new abilities related to the Kyuubi's powers. He might be able to communicate with the Fem Kyuubi on a deeper level, leading to an interesting dynamic between them. For example, they could team up to protect the Hidden Leaf Village in a more efficient way, using their combined fox - like skills.
In many Naruto fanfictions, the concept of Naruto becoming the Nine - Tailed Fox can be really interesting. It could potentially change the entire dynamic of the story. For example, his relationships with his friends and foes might be completely different. He might be seen as a more dangerous and unpredictable force, which would lead to different reactions from characters like Sasuke or Kakashi.
One possible plot could be that Naruto, as a fox, has to navigate the Hidden Leaf Village in a new form. He might struggle to communicate with his friends at first, but then discovers new ways to convey his thoughts, like through telepathy. Another idea is that he uses his new fox form to explore areas of the forest that were previously off - limits to him as a human. This could lead to him finding ancient secrets or new forms of chakra.
His relationship with Sakura would change a lot. Sakura might be initially scared of Naruto's fox form, but as she realizes it's still him inside, she would start to see him in a new light. She could become more protective of him. With Kakashi, Kakashi would be more cautious and observant, trying to figure out how to help Naruto control his new form. And with his rivals, they might either be more envious or more afraid of him now that he has this unique transformation.
Maybe Naruto is cursed by an enemy. As a fox demon, his appearance would change drastically. His hair could become more like a fox's fur, and he might grow a tail or two. His personality could also be affected. He might become more mischievous like a fox, but still retain his core values of loyalty and friendship. He would then have to find a way to break the curse while dealing with the changes in himself.
Naruto might gain new physical abilities like enhanced speed and agility as a fox. He could run faster through the forests and jump higher. The Fem Kyuubi could be his mentor in using these new skills.
His relationship with Kurama would definitely change. Instead of being two separate entities, they might have a more equal and symbiotic relationship as Naruto is now also a fox - like being. With his friends, they might initially be confused or even a bit scared. For example, Sakura might be shocked at first but then become very protective. And with his enemies, they might underestimate him in this cute fox - kit form, which could be an advantage for Naruto.
One possible plot twist could be that Naruto, as a fox kit, discovers he has unique powers related to his new form that are different from his normal ninja abilities. For example, he might be able to communicate with all fox - related spirits or creatures in the Naruto world. Another plot twist could be that the other characters don't recognize him at first, leading to some really interesting and comical situations. Maybe Sasuke tries to attack him thinking he's a wild fox, but then realizes something is off about this 'normal' fox.
His bond with Sasuke would take a new turn. Sasuke might see Naruto as an even greater rival now. He might be envious of Naruto's new powers on one hand, but also want to help him master them on the other. As for Sakura, she would be worried about Naruto. She would try to find medical jutsu to help him if there are any negative side - effects from becoming a fox demon.