Well, in certain fanfic ideas, there might be a situation where Kakashi is on the verge of death and he decides to pass on his Sharingan to Naruto. He could use some kind of secret technique that allows him to transfer the ocular powers to Naruto so that Naruto can have an extra power boost in his battles and for the protection of the village. This would be a very selfless act on Kakashi's part, considering how important the Sharingan is in the Naruto universe.
Perhaps in the fanfiction, there is a unique bond formed between Naruto and Kakashi during a very intense and life - threatening situation. This bond could be so strong that it enables a spiritual or chakra - based connection which results in Kakashi's Sharingan being transferred to Naruto. It could also be part of a prophecy or an ancient power transfer ritual that was long forgotten but gets re - activated in this particular scenario.
In some fanfictions, it could be due to a special jutsu gone wrong. Maybe a jutsu that Kakashi was using to transfer some of his chakra to Naruto for a mission accidentally transferred his Sharingan power as well.
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.
In some fan theories, it could be due to a unique chakra interaction. Maybe the Kyuubi's powerful chakra somehow mutates Naruto's own ocular abilities and triggers the emergence of the Sharingan. But this is just a wild fanfiction idea.
He might have increased visual abilities. For example, he could see chakra flow more clearly, which would be a great advantage in battle.
The consequences could be far - reaching in the fanfiction. Naruto's relationship with Kakashi might change. There could be a deeper sense of respect and a new kind of bond formed because of this transfer. In terms of power, Naruto could unlock new jutsus or abilities that are related to the Sharingan. He might be able to combine his existing Rasengan techniques with the Sharingan - enhanced perception. This could make him an even more formidable opponent. However, it could also put a strain on his body. The Sharingan is known to consume a lot of chakra, and Naruto's body might need to adapt to this new power drain. If he overuses it, it could lead to exhaustion or even long - term damage.
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.
One way this could occur in the fanfiction is if there was some sort of genetic manipulation. Maybe a rogue ninja or a mad scientist found a way to combine Uchiha genes with Naruto's. Mikoto, being an Uchiha, had the Sharingan, and through this unethical genetic process, Naruto ended up with the Sharingan. This would also open up a whole new set of abilities and challenges for Naruto as he has to learn to control this new power which is very different from his normal chakra - based powers.
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.
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.
In the fanfiction world, it could be due to a deep emotional bond between Naruto and Sasuke. Their connection could be so strong that in a moment of extreme danger or a spiritual awakening, Sasuke's Sharingan essence is transferred to Naruto. For example, if Sasuke was on the verge of death and his chakra merged with Naruto's in a desperate attempt to save Naruto, the Sharingan could be part of that transfer. This would also add a whole new layer to their relationship and Naruto's character development as he would have to learn to control this new power.
Well, if Naruto gets Shisui's Sharingan in the fanfiction, it could greatly enhance his perception skills. He'd be able to see chakra flow more clearly, which would help him in combat. He might also be able to use some of the Sharingan - specific jutsus like the Genjutsu techniques related to it. This would make him even more formidable against opponents, especially those who rely on stealth or illusions.