In some fanfictions, it could be through a special jutsu or ritual. Maybe Itachi, before his death, transferred his Sharingan to Naruto in a unique way, perhaps using a forbidden technique that was known only to a few in the Uchiha clan.
One way could be through a powerful jutsu gone wrong. Maybe a jutsu that was meant to transfer Itachi's memories to Naruto accidentally transferred his Sharingan as well. In the world of fanfiction, there are often many creative and out - of - the - box explanations.
Naruto would gain the ability to copy jutsu. With the Sharingan, he could watch an opponent's movements closely and replicate their techniques. This would be a huge advantage for him in battles.
One possible fanfiction could be that Itachi, on his deathbed, decides to transfer his Sharingan to Naruto. He sees in Naruto the potential to change the Uchiha's fate and the ninja world. Naruto, with the Sharingan, gains new abilities like enhanced perception and the ability to copy some jutsus more easily. He uses this new power to better understand the Uchiha and bridge the gap between them and the rest of the village.
I really liked 'Itachi's Hidden Truths'. In this fanfic, the author gives a different perspective on Itachi's actions. It shows how his Sharingan abilities were not just for combat but also for protecting those he cared about in his own, often misunderstood, way.
One possible scenario in such a fanfic could be that Itachi, seeing Naruto's potential and his pure heart, decides to entrust Naruto with his Sharingan. This could potentially give Naruto new abilities and a deeper understanding of the Uchiha clan's power. It might also create a unique bond between Naruto and the memory of Itachi, leading to new storylines where Naruto uses the Sharingan's powers in unexpected ways.
A good Naruto Sharingan Itachi fanfic should have a deep understanding of Itachi's character. His motives, like protecting Konoha at all costs, should be well - explored. Also, the power of the Sharingan should be accurately depicted, for example, showing how he could use genjutsu with it.
They could develop a mentor - mentee relationship. Itachi uses his knowledge of the Sharingan to teach Naruto new combat techniques. As they train together, they bond over their shared experiences of loss and their desire to protect the people they care about. Naruto might also help Itachi come to terms with his past actions and find some peace within himself.
I'm not sure specifically what that particular fanfic is about as there could be many interpretations. It might involve Sakura from the Naruto universe somehow obtaining the Sharingan, which is a powerful dojutsu. Maybe it could be about her newfound abilities, how it changes her relationships, or her role in battles with this new power.