In the fanfiction, after getting the Rinnegan from the Kyuubi, Naruto's relationships could change. His friends might view him differently, some with awe and some with concern. His enemies would definitely be more cautious of him. On a personal level, Naruto might face new internal struggles as the Rinnegan could come with a different way of seeing the world, perhaps making him more aware of the darker aspects of the ninja world that he hadn't noticed before. And of course, his combat abilities would be enhanced, allowing him to take on stronger opponents and protect his village in new and more effective ways.
He might become much more powerful. With the Rinnegan, he could gain new abilities like the Six Paths powers, which would make him a force to be reckoned with in battles.
One consequence could be that he is ostracized or feared by some in the ninja world. The Rinnegan is a very powerful and somewhat feared dojutsu. People might be suspicious of Naruto's new power and how he got it from the Kyuubi. Also, Naruto himself might struggle with the new power, having to learn how to control it properly to avoid accidentally causing harm.
He would likely become extremely powerful. His combat abilities would be enhanced significantly as the Rinnegan gives access to powerful jutsus. He could also gain new insights into the nature of chakra and the world around him.
In some fanfiction concepts, it might be due to a unique chakra interaction. Maybe the Kyuubi's powerful and ancient chakra somehow triggers a latent ability within Naruto that results in the manifestation of the Rinnegan. It could also be part of some kind of prophecy or destiny within the fan - created world of the story.
In some fanfiction concepts, the chakra of the Kyuubi is not just pure fox chakra but also contains remnants of the Sage of Six Paths' power. Since the Rinnegan is related to the Sage of Six Paths, when Naruto reaches a certain level of power and harmony with the Kyuubi, the dormant Rinnegan - like power within the Kyuubi's chakra awakens in Naruto. This could be a result of Naruto's strong will and his journey to master the Kyuubi's power which eventually leads to him obtaining the Rinnegan.
Naruto's perspective on the ninja world could change. With the Rinnegan, he would see things in a different light, both literally and metaphorically. He might have to deal with new enemies who are attracted to his new power or new responsibilities that come with such a powerful dojutsu. His relationships with his friends and allies could also be affected as they may view him differently now that he has this extremely powerful ability.
One consequence could be that Naruto becomes even more powerful. He can use the abilities of the Rinnegan, like the Six Paths techniques, which would make him almost unbeatable in battle. This would change the power dynamics in the ninja world significantly.
It could also be a situation where Naruto's connection to Hagoromo is deepened in the fanfiction. For instance, Naruto might have a vision or a spiritual encounter with Hagoromo. During this encounter, Hagoromo realizes that Naruto is the key to bringing true peace to the ninja world. So, he imparts the power of the Rinnegan to Naruto to help him achieve this grand goal. This would be a more complex and involved process, perhaps involving Naruto learning about Hagoromo's past and his own role in the grand scheme of things.
In some fanfiction concepts, there could be a spiritual or mental connection established between Naruto and Nagato. Since Naruto has this unique ability to understand and connect with people on a deep level. Through this connection, Nagato might pass on the power of the Rinnegan to Naruto. It could be like a transfer of not just the physical power but also the knowledge and understanding that comes with the Rinnegan.
In some fanfictions, it could be through a strange and powerful jutsu transfer. Maybe Madara, on the verge of defeat, decides to transfer his Rinnegan power to Naruto for some unforeseen reason, like seeing a new path for the ninja world in Naruto.
Another common theme is the relationship between Naruto and the fem Kyuubi. It could be a partnership, a friendship, or something more complex. The story often explores how they interact and grow together with this new situation of the fem Kyuubi having the Rinnegan.
In a fanfiction scenario where Naruto has Rikudou Sennin's powers, Kyuubi's chakra, and the Rinnegan, his power level would skyrocket. The Rikudou Sennin powers would enhance his understanding of chakra and life itself. The Kyuubi's chakra would boost his physical and chakra - based abilities even more. And the Rinnegan? That would open up a world of new jutsu possibilities. He could potentially reshape the Naruto world as we know it, perhaps even finding new ways to bring peace between the villages.