In addition to Naruto and the fem Kyuubi, there could be other characters like Sasuke. Sasuke might notice the changes in Naruto and try to save him from the corruption. Or Kakashi could also be involved, as he is Naruto's teacher and might sense something is wrong with Naruto and try to intervene.
Obviously Naruto and the fem Kyuubi would be the main characters. Naruto is the one being corrupted and the fem Kyuubi is the one causing the corruption.
Well, one possibility could be that the female Kyuubi's influence changes Naruto's personality. Maybe she makes him more aggressive or self - centered in the fanfiction.
Well, in some 'Naruto corrupted by fem Kyuubi' fanfiction, a great plot twist could be that the fem Kyuubi is actually a part of a larger prophecy that Naruto was unaware of. The corruption she brings is a necessary step in fulfilling this prophecy. It could also be that the fem Kyuubi's true form is not what it seems, and when Naruto discovers this, it completely changes his perception of her and their relationship. For instance, she might be a reincarnation of an ancient and powerful being, and her 'corruption' of Naruto is a way to awaken his latent powers related to that ancient being.
Obviously, Naruto would be the main character. Since it's about him being the new Kyuubi. And his friends like Sasuke, Sakura, Kakashi would also be important characters. They would likely be involved in how they react to Naruto's new state and how they support or oppose him.
Naruto is surely the central figure in this fanfiction as it's about his role as the father of the Kyuubi. The Kyuubi is essential as well. Additionally, characters like Jiraiya might be included. Jiraiya could play a role in guiding Naruto in this new aspect of his life, considering his relationship with Naruto in the original series. Other characters such as the Hokages could also be involved, maybe to give their perspective on this extraordinary situation.
The main characters would be Naruto and the Kyuubi. However, characters like Jiraiya could also be significant. Jiraiya, being Naruto's teacher, might have left behind some knowledge or clues that Naruto uses to figure out how to free the Kyuubi. And of course, Sasuke could be involved too. Maybe Sasuke has his own reasons for either helping or hindering Naruto's attempt to free the Kyuubi, which could add more drama to the story.
Another potential antagonist could be an inner demon within Naruto that is a manifestation of the Kyuubi's corruption. This inner demon could constantly be battling Naruto's good side, trying to take over completely. And there could be characters who misunderstand Naruto's situation and side with the forces that are trying to 'contain' or 'destroy' Naruto because they believe he is a lost cause due to the Kyuubi's corruption.
In addition to the well - known characters, there could be new characters introduced in the fanfiction. Maybe there are some ancient ninja clans who have knowledge about the 'fem Kyuubi' and they send their representatives to interact with Naruto. These new characters could bring in new plot twists and conflicts. For example, they might try to manipulate Naruto to use the 'fem Kyuubi' for their own purposes, which would put Naruto in a difficult situation where he has to decide who to trust.
Obviously, a female version of Naruto would be the main character. She would be at the center of the story, dealing with the consequences of the experimentation.
Kakashi could be involved as well. As Naruto's mentor, he would likely be concerned about Naruto's well - being and how he is handling the fusion. He might try to guide Naruto in controlling the power and also protect him from those who would seek to take advantage of his new - found strength.
Obviously Naruto and Kyuubi are the main characters. Naruto is the one making the deal, and Kyuubi is the one with whom the deal is being made.