A character who is a hybrid of two different clans, one with the Shikotsumyaku and the other with the Sharingan. This would give them a unique perspective and set of skills, making for an interesting main character.
How about a former villain who has been reformed and now has both Shikotsumyaku and Sharingan? They could be on a journey of redemption, using their powers for good instead of evil. Their past as a villain would add depth to their character as they struggle to be accepted by the other ninjas. In the Naruto world, redemption arcs are always interesting, and with such powerful abilities, it would be exciting to see how they use them in their new path.
It might also be Itachi. Imagine a scenario where Itachi's actions before his death somehow lead to his Sharingan being abandoned or lost in a different way than in the original story. This could open up a whole new narrative about his legacy and the impact it has on the Naruto world.
Sakura could be an unexpected character to have the Sharingan. It would completely change her character dynamics. She could use it to enhance her medical ninjutsu, seeing the internal body structure more clearly. Also, she could become a more formidable fighter, using Sharingan - based genjutsu to her advantage.
Another option could be Kakashi. Suppose he is banished because of some incident related to his Sharingan. He has so much history and experience, and seeing him outside of the village structure, relying only on his Sharingan and his wits, would make for a great story. He could also have flashbacks to his past experiences with the Sharingan while dealing with the challenges of being banished.
One idea could be a story where a character with both Shikotsumyaku and Sharingan abilities has to face a new, powerful enemy that can nullify their individual powers. So they must find a way to combine their abilities in an unexpected way to defeat the foe.
A new character could be a young Uchiha who has just awakened their Sharingan but is very shy and inexperienced. They enter the Chunin Exams and are constantly underestimated because of their quiet nature. But as the exams progress, they start to show amazing potential with their Sharingan, for example, being able to quickly analyze and copy complex jutsu. Another interesting character could be a non - Uchiha who has studied the Sharingan extensively and has developed techniques to counter it. This character would add an interesting dynamic to the Chunin Exams as they would be a threat to the Uchiha participants.
It could be Sasuke. Since he already has the Sharingan and later acquires the Rinnegan, he has a natural connection to both powerful eyes. A story could focus on his further adventures and how he uses the combined powers of the eyes in different situations.
A new character could be created as the main character. This character could be an orphan who discovers they have a single Sharingan eye, and they don't know where it came from. They then embark on a journey to find out about their heritage and the origin of their eye. Along the way, they meet various Naruto characters and learn about the power and responsibility that comes with the Sharingan. They might face challenges from both those who want to steal their eye and those who fear its power.
It could be Sasuke. In many Naruto - related stories, Sasuke has the Sharingan and is often the target of others' tricks or manipulations due to his complex personality and his power.
A new character could be introduced as a Sharingan master. For example, a wandering ninja who has been secretly studying the Sharingan for years. He might have no allegiance to any village and travels around, looking for worthy pupils to inherit his knowledge. He could have unique techniques related to the Sharingan that no one has seen before.
I'm not sure specifically which 'shikotsumyaku naruto fanfic' you're referring to. But it could be Kimimaro. Since he is the most well - known character with Shikotsumyaku in the Naruto universe, he might be one of the main characters in the fanfic.