A new character could be the main character. For example, a young orphan who is discovered to have a rare genetic trait that gives him the potential to develop both the Sharingan and Rinnegan. This character would then have to learn about the ninja world and his powers while facing various challenges and making new friends and enemies.
It could be Sasuke. Since he already has the Sharingan and later acquires the Rinnegan, he has a natural connection to both powerful eyes. A story could focus on his further adventures and how he uses the combined powers of the eyes in different situations.
Naruto could also be the main character in a different kind of story. What if through some strange chakra experiment or a divine encounter, Naruto is given the ability to use the Sharingan and Rinnegan temporarily? This would change his fighting style completely and lead to a whole new set of adventures as he tries to understand and control these new powers.
When it comes to character development in Naruto fanfic involving the Sharingan and Rinnegan, these eye - powers can be a great catalyst. A character who acquires the Sharingan might start to become more isolated as they struggle with the new power and the secrets it holds. For example, they could be afraid of losing control. With the Rinnegan, a character could develop a god - like complex. They might see themselves as above others due to the immense power. This can lead to internal conflicts and growth throughout the fanfic.
The Sharingan and Rinnegan are iconic in Naruto fanfic. The Sharingan's different levels, from one - tomoe to three - tomoe and then the Mangekyou Sharingan, offer a wide range of creative possibilities. Fanfic writers might explore the emotional toll of using the Mangekyou Sharingan, like Itachi did. Regarding the Rinnegan, it's often associated with the Sage of Six Paths. In fanfic, it could be used to bring back ancient powers or create new forms of ninjutsu. These two eye - powers can be combined in fanfic in ways that the original series might not have fully explored, making for exciting reading.
In a fanfiction, Naruto might obtain the Rinnegan and Sharingan through a unique encounter. For example, he could stumble upon a dying Uchiha who transfers his Sharingan to Naruto in a moment of desperation. As for the Rinnegan, it could be related to his connection with the Sage of Six Paths. Perhaps the Sage's spirit, seeing the great need in the ninja world, bestows the Rinnegan upon Naruto. It could also be a result of some sort of genetic experimentation gone wrong but in a way that gives him these powerful eyes instead of harming him.
Well, the plot could involve a character who has both the Sharingan and the Rinnegan. Maybe Naruto somehow gains the Rinnegan in addition to his own powers. He could use the abilities of the Sharingan, like predicting movements and copying jutsus, along with the Rinnegan's power to control the six paths. This would create a really powerful and unique situation in the Naruto universe. He might face new enemies that are only a threat to someone with such combined powers.
Sasuke could also be the main character. Given his connection to powerful eyes in the Naruto series, if the Rinnegan was abandoned, Sasuke's role would change significantly. He would have to re - evaluate his own power and place in the ninja world, which could make for a really interesting story with him as the main focus.
It could be an unknown Uchiha who was overlooked in the main story. Maybe they were born with the Rinnegan but due to some political unrest in their village, they were forced to hide their power and were thus neglected. In the fanfiction, they could come out of hiding and shock everyone with their Rinnegan - based abilities.
Another option could be Kakashi. Suppose he is banished because of some incident related to his Sharingan. He has so much history and experience, and seeing him outside of the village structure, relying only on his Sharingan and his wits, would make for a great story. He could also have flashbacks to his past experiences with the Sharingan while dealing with the challenges of being banished.
It might also be Itachi. Imagine a scenario where Itachi's actions before his death somehow lead to his Sharingan being abandoned or lost in a different way than in the original story. This could open up a whole new narrative about his legacy and the impact it has on the Naruto world.
Sasuke could be a great main character. He already has the Rinnegan in the Naruto series. Imagine him in the Avatar world, using his Rinnegan - enhanced skills to learn about the elements and become an avatar - like figure, but with his own dark and brooding personality.
It could be an original character. Maybe a young ninja from a small, forgotten clan who discovers they have the Mangekyo Sharingan. This character would have to learn about their power, its limits, and how to use it in a world full of powerful shinobi.