Perhaps there are some individuals who simply want to break the norms in a very extreme way in the fanfiction world. They might think that by creating such a controversial concept, they can attract attention. But this kind of attention - seeking through unethical or inappropriate means is not acceptable in the overall fan community. The fanfiction should be a place to expand on positive aspects of the original story, like friendship, growth, and heroism, rather than creating such negative power - play scenarios.
Some people might create such fanfiction out of a misinterpretation of the characters' relationships. They may want to explore extreme or 'edgy' scenarios without considering the ethical implications.
Since the idea of one character becoming another's'slave' is not in line with positive values, it's not a good idea to promote or discuss such fanfiction in detail.
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.
Some people might create such fanfiction for shock value. They want to stand out by coming up with the most extreme and unexpected ideas. It could also be a form of exploring the 'dark side' of a character, taking a well - loved hero like Naruto and twisting his character into something completely unrecognizable. Another reason could be that the writer has a very different and perhaps warped view of the Naruto universe and wants to express that through this very abnormal concept.
One possible reason could be extreme loneliness. Naruto has always faced some degree of isolation in the original story. In a fanfiction, this could be exaggerated to the point where he feels there's no way out and becomes suicidal. Another reason might be the failure to protect his loved ones. If in the fanfiction, he fails to save his friends or the village multiple times, the guilt could be overwhelming.
There's a chance that it could be a group of rogue ninjas. They want to use Anko's new position as Naruto's slave to infiltrate Konoha. They might be after some secret technique or valuable information. Naruto and Anko must work together to expose this group and save the village while also dealing with Anko's slavery situation.
Perhaps there is a group in the ninja world that believes slavery is wrong and they see Kin's situation as unacceptable. They would be the antagonists in the sense that they oppose Naruto's ownership of Kin, even if Naruto has good intentions. They might try to rescue Kin and this could lead to conflicts between them and Naruto. Also, there could be some of Kin's old allies who don't want her to be subservient to Naruto and they might cause trouble as well.
Well, Naruto would face quite a few challenges as Mikoto's father. Firstly, he has his own reputation and duties as a hero of the village. Balancing his time between being a father and fulfilling his village responsibilities would be tough. Secondly, Mikoto is from the Uchiha clan which has a dark history. Naruto would need to make sure Mikoto doesn't get influenced by any negative Uchiha ideologies. He'd also have to deal with the fact that Mikoto might inherit some of the Uchiha's pride and stubbornness, which could lead to clashes between them as she grows up.
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.
Perhaps the discovery of some dark secrets about the ninja world could make him ruthless. For example, if he finds out that the village leaders have been using him or his friends for some immoral purposes all along. This new knowledge could shatter his world view and make him question all his previous beliefs, leading him to become a more ruthless individual who is out to change or even destroy the existing order.
Well, if Naruto becomes Mikoto, he would be a female in the body of Mikoto. He could bring his own values and experiences as Naruto. This could potentially change the relationship dynamics within the Uchiha clan. He may try to bridge the gap between the Uchiha and the rest of the village in a way that Mikoto might not have been able to do in the original story due to her own limitations and the circumstances of the time.