The fem Kyuubi might feel a sense of protectiveness. Seeing Naruto without his mask could make her realize how vulnerable he is. She may then use her powers to safeguard him from any potential threats that could take advantage of his exposed state.
One possible plot could be that Naruto's loss of sanity causes him to have a distorted view of the Fem Kyuubi. Maybe he sees her as both a threat and a source of power he can't control. This could lead to a conflict within himself as he battles his inner demons while also interacting with the Fem Kyuubi in unexpected ways. For example, instead of the usual relationship of cooperation or taming, he might try to completely dominate her, which would be a big shift from the normal Naruto we know.
Other characters in the Naruto universe might also be affected. For example, his friends like Sakura and Kakashi would notice the change in Naruto. They might try to help him, but their attempts could be in vain because of the complex situation with the Fem Kyuubi involved. This would create new tensions and storylines as they struggle to deal with a Naruto who has lost his sanity and the mystery of the Fem Kyuubi's role in it.
Well, he could start making really rash decisions. Maybe he'd attack his friends by mistake, thinking they were enemies. Since he's lost his mind, his usual judgment would be out the window.
If Naruto loses his mask in this fanfiction, it might change the power dynamics. His identity being more exposed could make him a target. The fem Kyuubi might have to step up and use her powers to protect him. This could lead to a closer bond between them, and they might start to rely on each other more in the face of new threats.
One great fem Naruto x fem Kyuubi fanfiction could be one that focuses on their unique bond. It might explore how they interact in a world where Naruto is female and the Kyuubi also takes a female form. For example, it could show them teaming up against common enemies and how their combined powers are different from the original story.
A new, unknown villain could be the cause. This villain might have a special power related to mind control or mental manipulation. They target Naruto because of his status as a hero in the ninja world. By making Naruto lose his mind, they could throw the entire ninja world into chaos.
The storyline might start with Naruto being put in a really difficult situation that causes him to lose his mind. Then, the female Kyuubi could be introduced as a key factor in his recovery. Maybe she has some special ability or knowledge that can help him get better.
If the Kyuubi loses its memory in the fanfiction, it could potentially change the entire Naruto storyline. For instance, Naruto may no longer have the same source of power that he once had. Instead, he might have to rely on his own natural talents and training more than ever. The Kyuubi, without its memories, could start to develop a new personality. It might become more curious and innocent, which would be a huge contrast to its previous menacing self. This would force Naruto to adapt and also give the other characters in the series new ways to interact with both Naruto and the Kyuubi.