Their relationship would likely become more complex. With the Rinnegan involved, they might have to rely on each other more for understanding its powers. They could become more protective of each other, knowing the power and the danger it brings.
One implication is that he becomes much more powerful. The Rinnegan gives him access to powerful abilities like the Six Paths techniques, which would change the power dynamics in battles in the fanfiction. He could now face stronger enemies more easily.
In many fanfictions, the Rinnegan and chakra chains are often intertwined in terms of power and function. The Rinnegan, being one of the most powerful ocular abilities in the Naruto universe, can potentially bestow special properties on the chakra chains. The chakra chains themselves might be a way to channel the raw power of the Rinnegan. For instance, they could be used to bind opponents while simultaneously draining their chakra through the Rinnegan's absorptive capabilities. This connection adds an interesting dynamic to the characters who possess both the Rinnegan and the ability to use chakra chains, making for some really cool and unique battle scenarios in fanfiction.
Yes, there are likely to be 'harry has the rinnegan' fanfictions out there. The idea of combining elements from different fictional universes, like Harry Potter and Naruto (where the Rinnegan comes from), is a popular concept in fanfiction. Writers often like to experiment with giving characters from one world the powers or traits of another.
Another possibility is that it's a result of some strange chakra experiment gone wrong (or right). Scientists in the Naruto universe are always dabbling in chakra research. Maybe an experiment meant to enhance her natural abilities instead gives her the Rinnegan, and she then has to learn to control it quickly to avoid being consumed by its power.
If Naruto got the Rinnegan, he might become more cautious. The power of the Rinnegan is so great that he would realize he needs to be more careful with it. He wouldn't be as brash as before.
It could be Sasuke. If he were to turn to the dark side in the fanfiction, his Rinnegan powers could be used to destroy Konoha. He has the potential to be extremely powerful and if he has some sort of vendetta or is influenced by some dark force, he might take his anger out on the village.
In fanfiction, one way to combine EMS (Eternal Mangekyou Sharingan) and Rinnegan powers could be through a powerful jutsu. For example, a character might create a new form of ninjutsu that draws on the unique abilities of both. The EMS could provide enhanced visual perception and the ability to cast powerful genjutsu, while the Rinnegan could offer control over different elements and the six paths techniques. They could be combined in a way that allows for teleportation between different dimensions, using the space - time manipulation aspects of both powers.
Well, at first it might cause some strain. His sister may feel overshadowed by Naruto's new power. But as time goes on, Naruto could use the Rinnegan to help his sister discover her own latent abilities. This would transform their relationship into one of mutual growth and support. He could use the powers of the Rinnegan to train her in unique ways, and she could in turn offer him emotional support, making their bond even deeper than before.
Well, perhaps the protagonist uses the powers of the Rinnegan in secret. He might train alone and develop unique abilities that others are unaware of, so that when the time is right, he can surprise everyone who has neglected him.