In some fanfictions, Naruto gets the Sharingan as a gift from a dying Uchiha. This Uchiha, realizing Naruto's importance in uniting the ninja world, gives him the Sharingan. Naruto then uses it to understand the Uchiha's pain better and tries to bridge the gap between the Uchiha and the rest of the village. He also has to train hard to master the different levels of the Sharingan, like the Mangekyo Sharingan which comes with its own set of risks and rewards.
A possible plot could be a time - travel scenario. Hana and Naruto are sent back in time to the era when the Sharingan was first created. They have to figure out how to get back to their own time while also dealing with the power struggles and conflicts of that era. Hana's Sharingan becomes a key factor in their survival, as they use it to outwit powerful enemies and make allies among the ancient clans.
A plot could be that a rogue ninja steals the secrets of both the Sharingan and Byakugan and tries to create an army of super - ninjas with artificial versions of these eyes. The main characters then have to track him down and stop him before it's too late.
Well, a plot might be that Naruto is experimented on by Orochimaru. Orochimaru, always interested in powerful abilities, tries to implant the Sharingan into Naruto. Naruto initially struggles with this new power as it's not native to him. But with his strong will, he begins to master it and uses it in ways no Uchiha has before. He could combine the Sharingan's visual prowess with his Rasengan, creating an even more powerful attack. For example, he might be able to see the chakra flow within an enemy more clearly with the Sharingan and then direct his Rasengan to target the weakest points.
One possible plot could be that Naruto, through some mysterious means, is given Sasuke's Sharingan. He then has to learn how to control it quickly as it starts to affect his perception of the world. He might see things in a different way, like being able to detect enemies more easily. Another plot could involve Naruto using the Sharingan to understand Sasuke better, seeing his memories and the pain that led him to become the way he is.
One interesting plot could be that Evil Naruto uses his Mangekyou Sharingan to manipulate the memories of the villagers. He makes them believe false things about their past and present, causing chaos in the village. For example, he could make them think that their friends are enemies, turning the village against itself.
One interesting plot could be Naruto being banished and then finding a hidden village of outcasts. He could learn new and unique jutsu there and form an alliance to take on threats to both his old and new homes. Another plot might involve Naruto being banished and having to prove his innocence from afar, all while befriending other exiled ninjas who were wrongly accused.
One possible plotline could be the main character having a unique form of the Sharingan that gives them powers beyond what is normal in the Naruto universe, like the ability to time - travel. This could lead to them changing the course of major events in the Naruto story.
One interesting concept could be the exploration of new jutsu combinations using the Rinne Sharingan. For example, creating unique space - time ninjutsu that surpasses what we've seen in the original series. Another might be delving into the backstory of how the Rinne Sharingan came to be in a particular fanfiction's universe, perhaps it was the result of a long - forgotten experiment.
In some fanfictions, a character from another dimension enters the Naruto world with the Rinne Sharingan. This new character's power throws the balance of the Naruto world off. The story could revolve around Naruto and his friends trying to understand this new power and either make an ally of the character or defeat them to restore peace in their world.
One interesting concept could be unique Sharingan abilities not seen in the original Naruto series. For example, a Sharingan that can not only predict movements but also manipulate time on a small scale.