In a fanfic where Naruto has Sharingan, he might use it to gain new insights into the history of the ninja world. The Sharingan can see the past of those it looks at. So Naruto could use this to uncover secrets about the founding of Konoha or the true nature of the tailed beasts. This would put him in a unique position, as he already has the Nine - Tails inside him. He could combine the power of the Sharingan and the Nine - Tails to become an even more powerful ninja and protect his village in ways no one expected.
One interesting storyline could be Naruto discovers he has Sharingan after a strange encounter with an ancient Uchiha artifact. This new power makes his enemies question his identity and alliances, and he has to struggle with the newfound power while still being true to his ninja way.
In a fanfic, Naruto could inherit the Sharingan from a long - lost relative. This relative could be an Uchiha who fell in love with an Uzumaki long ago. With the Sharingan, Naruto gains the ability to predict his opponents' moves more accurately. He uses this new power in combination with his Rasengan to create new and powerful jutsus, and he also has to figure out how to control the Sharingan's curse, which comes with its own set of challenges.
One interesting storyline could be Sakura somehow getting the Sharingan. Maybe she's involved in an experiment gone wrong that gives her the Sharingan's power. This would completely change her abilities and how she interacts with Naruto and the others.
Another plot idea is that Naruto gets a Sharingan in a parallel universe. In this universe, he has to learn how to control it quickly while also dealing with the different political situations. Since the Sharingan is so powerful, many might try to either use Naruto or take the Sharingan from him, creating a lot of action - packed and suspenseful situations.
One interesting storyline could be a young ninja who discovers they have an innate ability to master the Sharingan at an extraordinary rate. They might then face challenges from jealous rivals within their own village who fear their growing power. Another could be a Sharingan master who has lost their sight due to overuse of the Sharingan but discovers a new way to 'see' through chakra perception, leading to a whole new set of adventures.
One possible plotline could be Naruto unlocking the Mangekyo Sharingan through some strange and unforeseen means, perhaps a powerful jutsu backfires and gives him this new power. Then he has to struggle with controlling it while his friends are both amazed and a bit worried about this new development in him.
Another plot could be that the Sharingan is given to Naruto as a last - ditch effort to save the village. A dying Uchiha gives Naruto his Sharingan, and Naruto has to figure out how to incorporate it into his already powerful set of skills. He might have to deal with the jealousy or suspicion of some of his comrades who are wary of the Sharingan's power.
Well, in some 'naruto of the mangekyou sharingan fanfiction', there might be a plot where a character discovers a hidden power within the Mangekyou Sharingan that was previously unknown. This power could be related to time - like being able to freeze time briefly in a battle. Or perhaps a story where the wielder of the Mangekyou Sharingan has to make a difficult choice between using its power for good or succumbing to the dark temptations that often come with such a powerful ability. It could lead to an internal struggle that shapes the character's journey.
One possible storyline could be that Naruto receives Kakashi's Sharingan through some sort of magical or experimental transfer. This new power could make Naruto even more formidable in battle. He might start to see the world in a different way, with the Sharingan's abilities to copy jutsu and predict movements. This could lead to new training regimens as he tries to master the Sharingan's full potential while still relying on his own Uzumaki powers like the Nine - Tails chakra.
Yes, there are likely fanfics out there where Naruto has one Sharingan. Fanfic writers often come up with creative and alternative storylines, and this could be one of them. They might explore how Naruto got the Sharingan, what new abilities he could gain from it, and how it would change his relationships with other characters in the Naruto universe.
One interesting fanfic could be 'Naruto: The Dual - Eyed Avenger'. In this fic, Naruto's acquisition of the Rinnegan and Sharingan completely changes the power dynamics in the Naruto universe. His new abilities make him a force to be reckoned with, and he uses them to protect Konoha in ways no one expected.