Maybe a character who was thought to be a regular ninja but then has an unexpected encounter that awakens their Fourth Dojutsu. For example, a genin who is on a simple mission in an ancient ruin and suddenly activates the dojutsu. This character would be an underdog type, which could make for an interesting story as they learn to control their new power.
It could be a descendant of an unknown clan. This character might have been living in obscurity until they discover their latent Fourth Dojutsu abilities. They then enter the world of shinobi and start making a name for themselves.
A great plot might involve a character who has the Fourth Dojutsu but has to keep it a secret from everyone. As they struggle with this burden, they start to realize that there are dark forces that are aware of their power and are trying to manipulate them. This creates a lot of internal and external conflict for the character.
Well, one way could be through some super - rare and powerful jutsu that transfers the dojutsu abilities to him. Maybe a forbidden jutsu that was long forgotten but he stumbles upon it somehow.
He could get a Dojutsu that allows him to manipulate time. This would be a very powerful ability as he could slow down or speed up time during battles. For instance, he could slow down time to dodge an enemy's attack and then speed it up to counterattack.
Well, it could make him an even more powerful ninja. The Dojutsu might give him new abilities like enhanced perception, the ability to see chakra more clearly, or even some kind of special attack. For example, if it's a Dojutsu similar to the Sharingan, he could potentially copy jutsu more easily.
He might gain enhanced perception. This could allow him to see chakra flow more clearly, similar to how the Sharingan can. So in battles, he can anticipate his opponents' moves better.
He becomes more confident. Knowing he has this new power from the dojutsu makes him believe more in his abilities to face tough challenges.
One possibility is that he has the Tenseigan and the Ketsuryugan. The Tenseigan would grant him incredible power, such as the ability to control gravity. The Ketsuryugan could give him some sort of blood - related power, like the ability to manipulate his own or others' blood to some extent. This combination would make Naruto's character in the fanfiction very interesting, as he would have to learn to balance and use these two very different Dojutsu effectively.
In some fanfictions, Naruto might obtain all dojutsu through some kind of ancient inheritance. Maybe he discovers a long - lost scroll or a hidden temple that bestows upon him these powerful eye techniques.
One option is a new, original villain created just for this fanfiction. This villain could be someone who wants to rewrite history and prevent the Fourth Hokage from ever becoming Hokage. So they target Naruto as he is the son of the Fourth Hokage. They might have some sort of time - traveling or reality - warping powers.
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.