Perhaps the red - haired character with the Rinnegan is an outcast in the ninja world because of their strange appearance and power. They then form an unlikely alliance with Naruto and his friends to prove their worth and fight against a new threat that only their combined powers can defeat. This could involve a lot of character development for the new character as they learn about friendship and acceptance.
One plot idea could be a character with red hair and the Rinnegan being a long - lost descendant of an ancient and powerful clan. They could be on a journey to discover their true heritage and in the process, face off against powerful villains who want to use their unique powers for evil.
Another idea is that the red - haired Rinnegan wielder comes from a different dimension. In this dimension, the Rinnegan has different abilities compared to what is known in the Naruto universe. They end up in the main Naruto world by accident and have to find a way to get back home while also dealing with the chaos their presence causes. Naruto and the others are initially suspicious but gradually come to trust this new character as they realize they have a common enemy.
One idea could be a story where the character with the Rinnegan avatar has to navigate a world where the rules of chakra and bending are combined. For example, they might use the Rinnegan's powers to control different elements in a way similar to how avatars control them in the Avatar world.
Well, a plot could revolve around a Rinnegan - induced time - loop situation. A character, perhaps Sasuke, gets caught in a time - loop where he has to keep reliving a certain period in the Naruto story but with different outcomes each time due to the influence of the Rinnegan. He has to figure out how to break the loop and in the process, discovers new secrets about the Rinnegan and its origin. This could also lead to him changing the fate of some characters who died in the original story.
One plot idea could be Naruto discovers he has the Rinnegan during a particularly intense battle against a new, powerful enemy. His friends are initially shocked but quickly realize they need to adapt to this new power. Another idea is that the Rinnegan was secretly given to Naruto by an ancient entity as a last - ditch effort to save the ninja world from an impending doom that only Naruto can face with this power.
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 interesting concept could be the unique powers associated with the red rinnegan. Maybe it has powers that are different from the regular rinnegan in terms of combat abilities, like being able to manipulate a new type of energy or having a special form of genjutsu. Another concept might be how the character who possesses it interacts with other characters in the Naruto universe. They could either be feared or revered, and this would change the power dynamics among different ninja clans.
One interesting plot could be a character with the red rinnegan having the power to manipulate time on a small scale. For example, they can rewind a few seconds during a battle to avoid an attack or foresee an enemy's move. Another idea is that the red rinnegan gives the ability to communicate with ancient spirits of the Naruto world, which could lead to uncovering long - lost secrets about the origin of chakra.
Maybe the red hair is a result of a genetic experiment or a curse that is linked to the Rinnegan. In the fanfic, it could be explained that an ancient ninja tried to combine the power of the Rinnegan with a powerful fire - type jutsu. The experiment went wrong in a way that gave the character red hair and also altered the Rinnegan's abilities. For example, the Rinnegan might be able to absorb and redirect fire - based attacks more effectively because of this connection.
An interesting plot idea for Naruto fanfic might be to focus on the life of a minor character. For instance, what if we told the story of a genin who never made it to be a chunin but still had a significant impact on the village in some other way? Or a story where all the ninja abilities are suddenly switched among the characters, and they have to adapt to these new powers while still facing their usual enemies. This could lead to some really fun and unexpected character interactions.
One interesting plot twist could be that Naruto gets the Rinnegan not through his own power, but as a result of a sacrifice by an unexpected character, like a long - lost Uzumaki relative. This relative could have been secretly protecting Naruto all along and in a moment of great danger, transfers their Rinnegan - like power to him.
One idea could be a story where Naruto discovers a hidden jutsu that allows him to time - travel. He could go back to the time of the First Hokage and learn ancient ninjutsu techniques, and also try to prevent some of the future tragedies. Another plot could be about Naruto befriending an outcast ninja from another village who has a unique power. Together, they work to change the views of the shinobi world towards outcasts.