Well, it could start with Sasuke being in a really dangerous situation where he's about to lose his eyes but Naruto intervenes. In the process, some sort of jutsu backfires and Naruto ends up with Sasuke's eyes. This would cause a huge shift in Naruto's relationships. His friends would be both worried and curious. And Naruto would be on a journey to master these new eyes while also trying to find a way to give them back to Sasuke if possible.
If Naruto had Sasuke's eyes in fanfics, it might make him more brooding. The Sharingan has a lot of baggage associated with it in Sasuke's story, and Naruto might take on some of that darkness. But at the same time, he would also be more in tune with Sasuke's experiences, which could strengthen their bond in a different way.
One possible plotline could be that Naruto is somehow influenced by a dark power. This power makes him believe that by taking Sasuke's eyes, he can gain ultimate power to protect the village. So, he sneaks up on Sasuke when he's vulnerable and steals his eyes. But then, he realizes the horror of what he has done and has to deal with the guilt and the consequences from both his friends and the village.
In fanfics where Naruto has Sasuke's eyes, his abilities would be altered significantly. The Sharingan is known for its power in genjutsu, so Naruto might become more proficient in that area. He could use genjutsu to deceive his opponents in new and unexpected ways. Moreover, the Sharingan's ability to predict an opponent's moves would blend well with Naruto's already great combat instincts. This combination could make him nearly unbeatable in battle, as he would be able to anticipate attacks and counter them with his own powerful jutsus.
The main character of the book,"The Second Generation of the Wood Leaf," was a transmigrator. He became the experimental subject of the Thousand Hand Pillars and the Uchiha Spot. He had a Shura Eye and a White Eye. He was Sasuke's cousin. I hope you like my recommendation. Muah ~
Naruto might become more brooding. Sasuke's eyes are often associated with his more complex and sometimes darker emotions. With those eyes, Naruto could start to see the world in a different light, one that's perhaps more cynical. He might also become more isolated as he tries to figure out the new powers on his own, not wanting to burden his friends with his confusion.
At first, Sasuke would be filled with rage. His Sharingan was something he had cultivated and was a symbol of his Uchiha heritage. Naruto stealing it would be like stealing his very soul. He would immediately try to hunt Naruto down. But as he chases Naruto, he might start to think about the reasons why Naruto did it. He could consider if there was some greater threat that Naruto was trying to combat, but still, he would not be able to forgive Naruto easily and would demand his eyes back.
Naruto might protect Sasuke by using his physical strength. He's got those powerful jutsus like the Rasengan. If any enemy comes near Sasuke, Naruto can just blast them away with his attacks.
If Sasuke's sister was in the picture, Naruto and Sasuke's relationship might soften more quickly. Naruto would see another side of Sasuke through his sister. He might also feel more of a connection to Sasuke's family. Sasuke, on the other hand, would see Naruto's genuine care for his sister, which could make him trust Naruto more.