Well, perhaps Naruto, having grown up without his real mother, is seeking some kind of maternal connection. And the Kyuubi, being such a powerful and dominant force within him, fills that void. It could also be that Naruto senses a deeper, more primal bond with the Kyuubi, something that goes beyond just being a host and a tailed beast, and he associates that bond with a mother - child relationship.
Maybe Naruto is just teasing Neji. In the Naruto world, friends often playfully taunt each other. Naruto might have seen Neji do something that he thought was more like what a girl would do, like being overly cautious or having a particular grace in his movements. It could also be a random joke that Naruto came up with to get a reaction out of Neji.
It changes the emotional aspect. Naruto's relationship with the Kyuubi becomes more of an emotional one rather than just a power - related one. This can lead to different power - up scenarios. For example, instead of just overpowering the Kyuubi's power, he might gain power through a more harmonious and emotional connection.
One reason could be a misinterpretation of the Naruto - Kyuubi relationship. If a writer doesn't fully understand the journey of Naruto and Kyuubi towards mutual respect and cooperation in the original story, they might come up with this idea. Another possibility is that they are trying to create a new and edgy storyline that caters to a niche audience who likes to see extreme power imbalances in fanfiction.
One possible reason could be Naruto's out - of - control power. If in the fanfiction Naruto has some new and extremely powerful abilities that he can't fully manage, Sakura might see him as a monster out of fear. For example, if he accidentally causes destruction while trying to save the village.
One possible reason could be a misunderstanding. Maybe some false information was spread about his mother, making Naruto believe she had abandoned him. Another reason could be related to the secrecy around his mother. If he grew up feeling alone and not knowing about her, he might develop resentment.
One possible reason could be Kakashi's strict teaching methods while not always following his own advice. For example, he might tell Naruto to always be on time for training but be late himself sometimes.
One possible reason could be that the Kyuubi's power goes out of control completely. Since Naruto has the Kyuubi inside him, if he fails to maintain the balance, the Kyuubi's raw and unrestrained power might end up killing him.
In these fanfics, the relationship between Naruto and the other characters might also be affected. For instance, how Sasuke might react if he knew Naruto had such a unique connection to the Kyuubi. It can add new plot twists and character developments to the story.
It could be a way for fans to further explore the deep connection between Naruto and the Kyuubi. Since their bond is so strong in the original story, some might take it to an extreme with the'mate' concept, thinking about how their relationship could be on a more intimate level in a different, non - canon way.
Well, in some fanfiction concepts, it could be possible through some sort of magical or spiritual connection that was misinterpreted in the Naruto universe. Maybe there was a powerful jutsu in the past that bound Naruto's essence to the Kyuubi in a way that made it seem like he was its father in this alternate storyline.