Perhaps in the fanfiction, there is some kind of magic or special chakra that gets infused into Naruto. This foreign chakra could be related to the Sharingan's origin. It then triggers the activation within him. For example, if there is an ancient artifact that holds the essence of the Sharingan and Naruto comes into contact with it, it might start the process of activation.
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.
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.
One great fanfiction could be about Naruto and Sasuke growing up as brothers and discovering the power of the Sharingan together. They might face challenges like protecting their village from a new and powerful enemy. The Sharingan could give them an edge in battle, and their brotherly bond could be a source of strength for both of them.
Yes, in some fanfictions, Naruto might end up having Sasuke's Sharingan through various creative plot devices. For example, in a story where there's a powerful jutsu gone wrong that transfers Sasuke's abilities, including his Sharingan, to Naruto. This can lead to really interesting character developments as Naruto has to learn to control and use this new power.
One key element is the power dynamic. The Sharingan gives Sasuke a unique power, and how that power is balanced with Naruto's own strength is often explored. For example, in some fanfics, Naruto has to find ways to keep up with Sasuke's Sharingan - enhanced abilities.
One common theme is the power struggle. Since the Sharingan is a very powerful ability, many fanfictions explore how Naruto and Sasuke deal with the power that comes with it. For example, they might struggle with the temptation to misuse it or have to learn to control it.
In a fanfic, Naruto getting Sasuke's Sharingan could be part of a plot where Sasuke sacrifices himself to save Naruto. Before dying, he gives Naruto his Sharingan. Naruto then has to deal with the new power as well as the emotional weight of carrying a part of Sasuke. He could use the Sharingan to see through illusions more easily and even gain some of Sasuke's memories related to the Sharingan's usage.