Perhaps he could obtain the Rinnegan through some sort of ancient ritual or a gift from a powerful entity. And to become Hokage, he would need to prove himself worthy through his deeds and leadership skills, like protecting the village from a major threat.
There could be various ways for Naruto to get the Rinnegan in the fanfiction. It could be that he inherits it in a strange way, like through a connection with an old sage. Regarding becoming Hokage, he would start by taking on more responsibilities within the village. He'd participate in important missions and show his loyalty to the village. As he grows in power and influence, he would gradually be recognized as a suitable candidate for Hokage. And with the Rinnegan, he would have an edge over other potential candidates, as it gives him unique abilities that can be used for the protection and development of the village.
In the fanfiction, Naruto might get the Rinnegan as a result of some unforeseen event. Maybe he discovers a hidden power within himself during a life - or - death battle. As for becoming Hokage, he would have to earn the respect of the village elders and the people. He'd have to show that he has the wisdom and strength to lead. This could involve making tough decisions and showing his ability to handle difficult situations. He would also need to be a great example for the younger ninja in the village.
He could obtain it through a powerful curse. For instance, a long - forgotten enemy places a curse on Naruto that not only gives him the blue Rinnegan but also sets him on a path to either destroy the world or save it depending on how he uses the power.
He could obtain it through a unique chakra infusion. Maybe during a battle with a powerful enemy who has some connection to an ancient chakra source, Naruto is accidentally exposed to a golden - hued chakra that fuses with his own and transforms his eyes into the Golden Rinnegan.
It could be that in the fanfiction, Naruto is exposed to a special type of chakra or energy source. This energy source could be related to an ancient artifact or a long - lost power. As Naruto has always been at the center of extraordinary events, his encounter with this special chakra could be the catalyst for him to obtain the True Rinnegan. It might also be that his previous battles and experiences have slowly been building up to this moment, and this final push of some external or internal factor causes the True Rinnegan to emerge.
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.
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.
One possibility is that there was some sort of spiritual or chakra - based connection between Naruto and Nagato. Nagato, being the possessor of the Rinnegan, recognized Naruto's strong will and the fact that he was on a path to change the ninja world for the better. Through this connection, Nagato was able to transfer the power of the Rinnegan to Naruto. It could also be related to the nature of the Sage of Six Paths' power that was somehow involved in this transfer, as both Naruto and Nagato were related to the Sage in different ways.
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, Naruto might awaken the Rinnegan through a powerful jutsu overload. For example, if he combines a super - charged Rasengan with some ancient and forbidden chakra - based techniques. This could potentially trigger a genetic or chakra - system shift that results in the awakening of the Rinnegan.
Well, it could be due to a genetic anomaly that was dormant within Naruto all along. Maybe his Uzumaki and Namikaze bloodlines combined in a unique way as he faced extreme challenges in the fanfiction, which then led to the unexpected evolution of the Rinnegan. For example, if he was exposed to a strong and strange form of chakra during a battle with an extremely powerful enemy, this could be the catalyst for such a transformation.
In such a fanfiction, Naruto would be extremely powerful with the Rinnegan. He could use powerful jutsu like the Six Paths techniques. As Hokage, he would bring a new era of peace and strength to the village. His Rinnegan abilities might help in better defense against threats and also in diplomatic relations as other villages would fear his power.