In some fanfictions, it could be through a divine intervention by Kami. Maybe Kami sees Naruto's pure heart and his need for more power to protect the village. So, Kami decides to bestow upon Naruto the power of Madara's Sharingan as a way to give him an edge in battles against powerful foes.
It could have a huge impact on the balance of power in the ninja world. With Naruto having Madara's Sharingan, other villages might become more cautious or even hostile towards Konoha. This would lead to new political situations and alliances. Moreover, Naruto's training and growth would take a new direction. He would need to learn how to combine his existing abilities with the new powers of the Sharingan, which would be a complex and interesting process to explore in the fanfiction.
In fanfiction, it could be due to a strange encounter with a magical or ancient artifact. This artifact has the power to transfer the Sharingan's essence from Madara to Naruto. It might be a relic from an ancient battle between the Uchiha and some other powerful force, and when Naruto and Madara come into contact with it, the transfer occurs.
One possible fanfiction could be about a young ninja who discovers he has a special connection to Madara's Sharingan. Maybe he inherits some of Madara's latent powers through a mysterious family link. This could lead to him being hunted by those who want to use his power for evil or by those who fear it.
In fanfiction, if Naruto got the Sharingan from Madara, it would completely change his power dynamic. He would gain the abilities of the Sharingan like enhanced perception, the ability to copy jutsu more easily, and perhaps even access to some of Madara's unique Sharingan - based techniques. This would make him an even more formidable opponent and could potentially change the entire plot of the Naruto universe within the fanfiction world.
It could be Orochimaru. Since he has always been interested in obtaining powerful abilities, he might see Naruto with the Sharingan as a threat and try to take it for himself.
Well, one possibility is that Naruto's new Sharingan power could give him an edge in battles against stronger foes. He might be able to quickly analyze their moves and counter them more effectively.
In fanfiction, the 'kami' could be an original deity created by the author. This new 'kami' could have its own motives and reasons for giving a gift to Naruto. Maybe it's a kami that has been observing Naruto's journey and decides to interfere to help him achieve a greater purpose. It could be a kami associated with nature, like a kami of the wind or the fire, and the gift could be related to that element.
One possible thing that could happen is Naruto would gain new visual abilities. With the Sharingan, he might be able to copy jutsus even more effectively than before. The Sharingan could also potentially enhance his perception of his opponents' moves, making him an even more formidable fighter in battle. This could change the power dynamics in the Naruto universe significantly.
A fanfiction could focus on a character who is immune to the effects of Madara's Sharingan. This character could be a new type of ninja from a far - off land with a unique chakra nature that counteracts the Sharingan's genjutsu and other abilities. The story could be about how this character challenges Madara and changes the power dynamic in the Naruto universe.