An interesting plot would be if Sasuke's Sharingan starts to show some strange side - effects due to overuse, and Naruto, with his unique connection to the Sage of Six Paths (which has a link to the Rinnegan), has to find a way to heal Sasuke. In the process, they uncover secrets about the Uchiha clan and the origin of the Rinnegan that no one knew before. This could involve exploring different dimensions and meeting long - lost ancestors. The story could be filled with emotional moments as Naruto tries his best to save his friend and Sasuke struggles with his own power.
A cool plot could be that a new villain emerges who has the ability to nullify the powers of the Sharingan and Rinnegan. Naruto and Sasuke have to find a way to overcome this without relying solely on their eye powers. They might discover ancient techniques that their predecessors used before the existence of these eye powers.
One idea could be a story where Sasuke, with his Sharingan, discovers a new power related to the Rinnegan that was hidden within Naruto all along. Maybe Naruto has some dormant Sage of Six Paths energy that when combined with Sasuke's powers, they can unlock a new level of strength to fight a powerful, unknown enemy.
Imagine a plot twist where the Sharingan and Rinnegan are not unique to the ninja world. In a fanfiction, it could be revealed that an alien race has similar powers. A character from Naruto's world travels to this alien planet and discovers that their understanding of these powers is completely different. They must then adapt to this new knowledge and use it to save both worlds from a common enemy that is drawn to the power of the Sharingan and Rinnegan.
The plot might involve Naruto with the Rinnegan being a bit of an outcast in the village at first because of the strange and powerful new dojutsu. Fem Sasuke could be the one to understand him and encourage him to embrace it. They could then go on a quest to discover the origins of the Rinnegan together, facing various challenges along the way, like ancient ninja traps and powerful, long - forgotten clans.
A plot development might involve Naruto struggling to control the Rinnegan at first. Sasuke, noticing this, believes he can defeat Naruto easily with his Sharingan. But as Naruto starts to master the Rinnegan, he shows new abilities that shock Sasuke. This could lead to a situation where they have to team up against a common enemy who is after the power of both the Rinnegan and the Sharingan. Or perhaps a prophecy is revealed that states only one of them can keep their dojutsu power and they must fight to decide who keeps it, leading to a moral and power - based struggle.
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.
Another plot could involve a forbidden jutsu that combines the powers of these three ocular abilities. Maybe a hidden scroll is discovered that details how to perform this jutsu, but it comes with a great cost. The main character has to decide whether to pursue this power despite the risks, which could lead to internal conflict as well as conflict with other characters who oppose this dangerous path.
One interesting plot idea could be a story where a character with both Sharingan and Rinnegan has to face an ancient evil that threatens the entire ninja world. This character could struggle with the power and the different abilities of both eyes as they try to master them in order to defeat the enemy.
One plot idea could be that Naruto and Sasuke discover a new power related to the Rinnegan that can only be accessed when they combine their chakra. Another could be a time - travel plot where they go back in time to prevent the creation of the Rinnegan in the wrong hands. Maybe they have to face an enemy who has a corrupted version of the Rinnegan powers and they must use their own understanding of the power to defeat them.
Well, it might be that there's a powerful enemy who can only be defeated if Naruto has the Sharingan. Sasuke, realizing this, decides to transfer his Sharingan to Naruto. In the fanfiction, Naruto would then have to deal with the new power. He might struggle at first to control it as it's not his natural ability. But as time goes on, he could use it to better understand Sasuke's perspective and strengthen their bond even more. He could also use it in battle, perhaps seeing his opponents' moves more clearly and countering them more effectively.
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.