For his teachers, like Kakashi, they would be on high alert. They would need to train Naruto to better control the transformation. This could create a more intense teacher - student relationship. Naruto's transformation also affects his relationship with the other Jinchuriki. They might see him as a kindred spirit or be jealous of his power, depending on their own experiences and personalities.
His relationship with the villagers could become more complex. Some might see him as a greater threat, while others who have come to know Naruto as a hero might be more accepting. His transformation could also lead to new alliances as some might want to use his power for their own purposes, which Naruto would have to navigate carefully to protect his relationships.
It could make his friends more cautious around him. For example, Sakura might be a bit more hesitant to get close, fearing the power of the Nine - Tailed Fox. But at the same time, some like Sasuke might see it as an opportunity to become stronger by sparring with Naruto in this new form.
There are fanfictions where the Nine - Tailed Fox has a split personality. One side is the fierce and powerful beast, and the other is a more gentle and understanding entity. Naruto has to deal with both sides, which creates a very complex and different kind of relationship compared to the original series. This can lead to some really interesting character development for Naruto as he tries to balance and understand this unique relationship.
Well, in some fanfictions, Naruto might start his journey after a particularly intense battle where he realizes the full potential of the Nine - Tailed Fox's power within him. It could be a fight against a strong enemy that makes him understand he needs to control the fox's power to protect his friends and the village.
When it comes to Sasuke, the Nine - Tailed Fox Faunus could be seen as a threat at first. But as the story progresses, they might find common ground in their pursuit of power and their desire to protect their own kind. The faunus could show Sasuke a different side of power, one that is more in tune with nature.
It can completely turn the plot around. If the story was about Naruto being in a tough situation against a powerful enemy, summoning the Nine - Tailed Fox could be the solution to that problem. It could be like a deus ex machina moment, but also very exciting for the readers.
In RWBY fanfiction, the concept of Naruto's Nine - Tailed Fox could be really interesting. One way it could be incorporated is by having a character in the RWBY universe inherit the power of the Nine - Tailed Fox somehow. Maybe a Grimm could be created that has similar characteristics to the Nine - Tailed Fox, like its powerful chakra - like energy. This would add a whole new level of danger and mystery to the RWBY world.
One way is to show how the transformation affects his relationships. Maybe his friends start to see him in a new light, and he has to work hard to maintain those relationships. He could learn more about loyalty and friendship as he tries to prove that he's still the same Naruto, even with the power of the Nine - Tailed Fox. This would enhance his character development in terms of his social and emotional growth.
He becomes more aggressive. The nine - tailed fox's nature seeps into Naruto, so he's quicker to anger and more likely to lash out. For instance, he might not think as rationally as he usually does when making decisions in battle or in dealing with his friends.
Obviously Naruto himself, as he is the one turning into the Nine - Tailed Fox. Sasuke would also likely be involved. He might be the one to try and reach Naruto when he is in his fox - form, either to fight him or to bring him back. Sakura too, she could use her medical ninjutsu to try and help Naruto if he gets injured during the transformation.
In fanfiction, when Naruto unleashes the Nine - Tailed Fox, it often leads to intense and action - packed scenes. Writers might explore the raw power Naruto gains, how it affects his relationships with friends like Sasuke and Sakura. For example, they could be in awe or even a bit scared of this new, more powerful Naruto.