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 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.
In this fanfiction concept, Naruto and Sasuke as brothers could lead to a very different Naruto universe. With Sasuke having the Sharingan, he could potentially use it to protect Naruto more often. Maybe they would train together in new ways, combining Sasuke's Sharingan - related jutsu with Naruto's Uzumaki power. For example, Sasuke could use his Sharingan to analyze Naruto's chakra flow and help him master new forms of the Rasengan faster.
In this kind of fanfiction, Itachi might use his powerful Sharingan abilities. He could perhaps create illusions to mislead Orochimaru and his minions, then quickly snatch Sasuke away. For example, he could make Orochimaru think that Sasuke is in a completely different location while he secretly approaches and rescues him.
In many fanfictions, Sasuke starts as a character full of anger and a thirst for revenge. But in the context of a relationship with Itachi, he begins to soften. He starts to see Itachi in a different light, beyond just the person who killed their clan. Itachi, on the other hand, is often portrayed as a complex figure with many secrets. In these fanfictions, his love for Sasuke makes him more vulnerable and human. For example, in some stories, he reveals his true motives to Sasuke, which changes their dynamic.
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.
Naruto might adapt by first trying to understand the basic functions of the Sharingan. He could start with the simple ability to see chakra flow more clearly. Since he has always been perceptive about people's emotions, he could use the Sharingan to read the emotions of his enemies through their chakra, which would help him in battles.