In a fanfiction, how does Naruto obtain the blue Rinnegan?

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.

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.

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.

It might be related to a connection with some powerful entity in the Wave arc. For example, if there's a secret shinobi from the past whose power is tied to the Rinnegan and Naruto somehow forms a bond with that power source, it could lead to the awakening. Also, the intense emotions and challenges he faces in the Wave arc might be a catalyst, pushing his chakra to a new level and awakening the Rinnegan.