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.
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.
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.
One interesting plot could be Naruto using the Rinnegan's powers in unique ways during battles. For example, he might combine the Rasengan with the Deva Path's ability to attract and repel, creating a new and powerful attack.
In this fanfiction, Naruto might gain incredible new powers. He could have enhanced control over all the elements and maybe even the ability to manipulate life and death like the true Rinnegan is often associated with in the Naruto lore. This would likely make him an even more formidable opponent and a great protector of the Hidden Leaf Village.
In this fanfiction, Naruto would become extremely powerful. With the Sharingan, he could gain abilities like predicting movements and copying jutsus more effectively. The Rinnegan would give him powers such as the Six Paths techniques. He might be able to use these newfound powers to better protect Konoha and face stronger enemies.
Well, if Naruto got the Rinnegan as a kid in fanfiction, it might make him a target for various enemies and force him to grow up faster. Also, it could completely rewrite his relationships with other characters.
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.