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.
One great fanfiction could be about Kakashi using his Sharingan to train Naruto in a special jutsu. Maybe he shows Naruto how to better perceive an opponent's moves by using the Sharingan's ability to analyze. This could lead to Naruto developing a new and powerful technique that combines his own chakra control with the insights from the Sharingan.
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.
Yes, there might be some fanfictions out there with such an unusual plot. However, it may not be a very common or mainstream concept in the fanfiction community. Fanfiction often explores creative and sometimes out - of - the - box ideas, and this would be one of them.
Kakashi would be deeply concerned. Given his relationship with Sasuke, he'd feel a strong sense of duty to save him. He'd use his extensive network of contacts within the ninja world to try and find out where Sasuke has been taken. He might also reflect on his past training with Sasuke and how he can use that knowledge to anticipate the kidnappers' moves. He'd be ready to face any danger or obstacle in his path to rescue Sasuke. And he'd be constantly thinking about Sasuke's safety and well - being during the whole process.
It would be very close. Kakashi would be like a father or an older brother to them. Naruto and Sasuke would respect and rely on him. They would probably have a more harmonious relationship with each other too, because Kakashi would be there to mediate any conflicts.
One way could be through words of wisdom. Kakashi has a lot of life experience and could share his insights with Sasuke, like how to deal with his inner turmoil and the path he should choose. For example, he might tell Sasuke that revenge isn't always the answer and that there are other ways to find peace.
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.
Yes, there are many. You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Naruto Eternal Sharingan Sasuke' and you'll find a bunch of them, but the quality may vary.
Well, in such a fanfiction, one possibility is that Naruto would inherit some of the Sharingan's powers through their brotherly bond. Since they are so close, Sasuke's Sharingan might react differently to Naruto. It could give Naruto an ability to see chakra in a new way, similar to how the Sharingan works. This would be a really cool addition to Naruto's existing powers and would make their battles more interesting.