Well, Naruto himself could be a main character even in a fanfiction about the Jagan Eye. He might be the one who discovers or has to deal with someone who has the Jagan Eye.
Sure. There are some great 'Jagan Eye Naruto Fanfiction' on fanfiction.net. You can search by the key words and browse through different stories. Some might focus on new adventures of Naruto with the added element of the Jagan Eye.
In some 'naruto jagan eye fanfiction', the Jagan Eye could be linked to an ancient prophecy. The character with the eye might be fated to either save or destroy the ninja world. This would create a lot of drama and moral dilemmas as they struggle with their destiny.
Naruto's character would also develop in terms of his relationships. His friends might view him differently, some with awe and some with a bit of fear. He would have to work hard to maintain those relationships. With his enemies, he would be seen as an even greater threat. But Naruto would use this new perception to his advantage. He would try to use the fear of his Jagan Eye power to deter potential attackers and also to broker peace deals when possible. He would grow into a more complex and mature character as he navigates the challenges of having this new power.
In a fanfiction, if Naruto has the Jagan Eye, it could change his relationships with his enemies too. For example, Orochimaru might be more interested in Naruto now. He could try to manipulate Naruto into using the Jagan Eye for his own evil purposes. Naruto, on the other hand, would be determined not to let the power corrupt him and would use it to protect the Hidden Leaf Village and the whole ninja world from new threats that are emerging because of his new power.
Many 'naruto jagan fanfiction' also have the theme of self - discovery. The characters with the Jagan usually have to figure out not only how to use it but also how it fits into who they are. For example, in 'Jagan and the True Self', the protagonist goes on a journey to understand how the Jagan is related to their inner self and their place in the Naruto universe.
One great 'naruto jagan fanfiction' is 'The Jagan's Ascent'. It explores the power of the Jagan in a really interesting way, with the main character learning to control it and facing off against new enemies.
Well, in some fanfictions, he might obtain it through a strange encounter. Maybe he stumbles upon an ancient relic during a mission that contains the power of the broken eye dojutsu and it somehow bonds with him.
It might have the ability to see through illusions that normal eyes can't. Since it's a dojutsu, even if it's broken, it could still have some enhanced visual powers. For example, it could detect the tiniest movements of an enemy, giving Naruto an edge in combat.