One possible plot twist could be that Naruto, upon getting Sasuke's Rinnegan, starts to see visions of the past and future of the Uchiha clan. This new power might make him question his own beliefs and the relationship between the Senju and Uchiha. He could see the events that led to Sasuke's decision to give him the Rinnegan and struggle with the responsibility that comes with this powerful dojutsu.
The plot could take a turn where Naruto, with Sasuke's Rinnegan, discovers a hidden power within the Rinnegan that was unknown even to Sasuke. This power could be related to the origin of chakra or a way to finally bring true and lasting peace to the ninja world. However, in order to unlock this power, Naruto has to face his darkest fears and insecurities, which are amplified by the Rinnegan's influence.
Maybe Naruto getting Sasuke's Rinnegan causes a rift in the ninja world. Other villages might see him as a threat now that he has this extremely powerful ability. His friends in Konoha could also be divided in their opinions. Some might trust Naruto completely, believing he'll use it for good, while others might fear that the power could corrupt him. And Naruto would have to deal with all these new tensions.
One possible plot could be that Naruto somehow inherits Sasuke's Rinnegan in a final battle against a powerful new enemy. This new power could cause Naruto to struggle with the dark nature of the Rinnegan while still trying to uphold his values of friendship and peace. He might have to learn new jutsu quickly and face the moral dilemma of using such a potentially dangerous power.
The curse mark could have a mind of its own. It starts to communicate with Naruto and Sasuke in their dreams, trying to manipulate them into doing its bidding. Naruto, being the optimistic one, tries to resist and turn the curse mark's power into something positive. Sasuke, however, is more tempted by the power it offers. This could lead to a rift between them as they have different approaches to dealing with the curse mark, and their relationship would be put to the test.
One possible plot twist could be that they face opposition from their respective clans who still hold grudges from the past. The Uchiha clan might not accept Naruto easily due to his connection to the Nine - Tails. Another twist could be that Sasuke discovers a new power within herself during their marriage that has unforeseen consequences for the village. Maybe it attracts enemies who want to steal that power.
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.
Perhaps there could be a rival who tries to break them apart. This rival could be someone from Sasuke's past who has a grudge against him and sees Sakura as a way to get revenge. They might spread false rumors about Sasuke to make Sakura question his loyalty.
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.
The fanfic could start with Naruto being exposed to a strange chakra during a battle with an unknown foe. This chakra mutates his own and results in him getting the Rinnegan. As a result, he gains the ability to understand and communicate with all forms of life, which is one of the Rinnegan's powers. Naruto decides to use this new power to broker peace between different ninja clans and villages. He uses the Animal Path to summon various powerful beasts to act as ambassadors of peace. However, there are still some rogue elements in the ninja world who see Naruto's new power as a threat and try to eliminate him, leading to an all - out battle where Naruto must use his combined powers, including his new Rinnegan abilities, to defend himself and his ideals.
If Naruto got the Rinnegan in fanfiction, it could completely change the power dynamics. For one, his combat abilities would skyrocket. He could use all the Rinnegan - related jutsus like the Six Paths techniques. This would likely make him even more of a force to be reckoned with against foes like Sasuke or any new threats. It might also change his relationships. For example, his standing among the shinobi villages could become even more dominant, as the Rinnegan is seen as a very powerful and rare dojutsu.
Another plot twist could be that an enemy uses their relationship against them. The enemy could spread rumors or false information to create chaos and turn the ninja world against them. Naruto and Sasuke would then have to fight not only to protect their relationship but also to clear their names and prove that their love doesn't mean harm to the ninja world.
One possible plot twist could be that Naruto's braces give him some sort of new power. Maybe they are made from a special chakra - conductive material. So when he uses his ninjutsu, the braces enhance his power output in unexpected ways. For example, his Rasengan could become even more powerful and have new properties like being able to change direction mid - flight. Another plot twist could be that the braces are part of a disguise by an enemy. They are actually a device to spy on Naruto and his friends. But Naruto discovers this and turns the tables on the enemy by using the braces' features against them. Also, it could be that the braces are a gift from a mysterious figure who has a connection to Naruto's past, and they hold the key to unlocking some long - forgotten family secret.