Well, perhaps in the fanfiction, the red rinnegan is a result of a forbidden experiment that combines different kekkei genkai. This new power source causes a stir in the ninja world, and the character with it has to deal with being hunted by various factions. They could also have the power to create portals to different dimensions that are full of unique and dangerous creatures, adding an element of exploration to the story.
A great plot idea for Naruto red rinnegan fanfiction could be that the red rinnegan is the key to restoring a long - lost civilization. The character with this eye power embarks on a journey to find all the pieces of a powerful artifact that was shattered and spread across the ninja world. Along the way, they face many challenges, make new allies, and learn more about the true nature of the red rinnegan and its connection to the ancient civilization.
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.
Perhaps a plot where Naruto's Rinnegan is a result of a curse placed on him by an ancient evil. As Hokage, he has to not only fight against external threats but also the inner struggle of controlling the power of the Rinnegan without succumbing to the curse. He could learn about the origin of the Rinnegan from old scrolls and seek the help of sage-like characters to overcome the curse.
Well, a cool plot for a Rinnegan Naruto crossover fanfiction could be that there is a rift between the Naruto world and a world where the Rinnegan is more common. Naruto gets pulled into this other world and has to adapt to the different power system there. He meets characters who have mastered the Rinnegan and has to learn from them to find his way back home. Along the way, he discovers a connection between the two worlds that was hidden for centuries.
One plot idea could be a story where Naruto discovers he has the Mokuton and Rinnegan abilities due to some ancient curse or prophecy. He then has to learn to control these new powers while facing off against a new, powerful enemy that is immune to normal jutsu. Another idea is a fanfic where Naruto uses his Mokuton and Rinnegan to travel to different dimensions to find a way to save the Hidden Leaf from a looming disaster. Or perhaps a story where he has to team up with old enemies who are also intrigued by his new powers and together they form an uneasy alliance to fight a greater evil.
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.
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.
Perhaps the OC is a healer who is the only one who can keep Naruto's body stable when he overuses his Rinnegan. Their relationship starts as a necessity but then develops into a deep friendship or more. They get involved in a conflict where Naruto has to use his Rinnegan to save the OC's clan from destruction, and in the process, they learn more about the secrets of the Rinnegan and their own destinies.
A plot idea could be that a group of students suddenly develop Rinnegan powers during a zombie outbreak in their high school. They must then figure out how to use these powers to not only survive but also find a cure. Another idea is that a Naruto - like character from another dimension arrives in the Highschool of the Dead world with Rinnegan and tries to teach the survivors ninjutsu to fight the zombies.
A third plot idea is that Naruto is given the Rinnegan as a last resort to save the ninja world. An old sage or some kind of divine being bestows it upon him. But with the Rinnegan comes a prophecy that he will either save or destroy the world. Naruto then has to battle his inner demons as well as external foes, all while trying to understand the true nature of the Rinnegan and its place in his destiny.
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.