It could be a new character created by the fanfic writer. Maybe a young orphan who discovers their seal - making talent by accident.
Perhaps it could be one of the existing minor characters from the Naruto series who has always had an underlying potential for seals but was never fully explored in the original story. For example, that one student in the Ninja Academy who was always doodling strange symbols that turn out to be the basis for advanced seals.
Perhaps there is a wise old seal master who takes the prodigy under their wing. This character could have a lot of knowledge about the history and secrets of seals, and they would play an important role in the prodigy's growth. Additionally, there could be some antagonists, maybe a group of rogue ninjas who want to steal the prodigy's seal knowledge for their own evil plans.
There's also a chance that the main character could be a completely new character from a minor clan in the Naruto universe. This character could have some hidden bloodline limit that makes them a prodigy in the ANBU. They might start as an underdog but quickly rise through the ranks due to their exceptional skills and intelligence.
In a 'naruto seal prodigy fanfic', it may tell the story of a young ninja who has a natural gift for seals. This prodigy might start off as an unknown in the ninja world but quickly rises to prominence because of their seal - related abilities. They could be mentored by an old and wise seal master or they might be self - taught. Their skills could attract the attention of both good and bad forces in the Naruto universe. They might get involved in a plot to protect a powerful seal from falling into the wrong hands or use their seal knowledge to unlock ancient secrets.
Since it's a fan - made story, the main character could be anyone. It could be an OC (original character) designed to be the center of this forgotten prodigy narrative. They could have a backstory full of hardships that led to their being forgotten. Or, as I said before, it could be a familiar Naruto face but with a whole new story arc that focuses on their previously unacknowledged prodigious nature.
It could be an original character created by the fanfiction author. This character might have a special background or power that makes them a ninjutsu prodigy.
Maybe an entire rival village decides to target the prodigy. They see the potential threat that the prodigy poses to their own village's dominance, so they send their best ninjas to take the prodigy down.
It could be an old enemy of the village who has been waiting for the seal to break. Maybe someone who was imprisoned by the same seal long ago and now wants revenge on the village for sealing them away.
The title 'naruto seal master lemon fanfic' gives some clues but doesn't clearly define the main character. The seal master is a likely main character as they are associated with the important concept of seals in Naruto. But 'lemon' could also take on the main role. It might be a story where Lemon is a unique individual with a special connection to the seal master, and the story is told from Lemon's perspective, making Lemon the main character. Or perhaps the story focuses on their relationship equally, in which case there may not be a single 'main' character in the traditional sense.
It could be a new character, like a young genin who has a natural affinity for seals. This character stumbles upon the mystery of the five - pronged seal during a routine mission in an old, abandoned temple. They are curious and determined, which drives them to uncover the secrets of the seal.
Hinata could be a great main character. Since she comes from the Hyuga clan, the Caged Bird Seal has a direct impact on her family. Her journey to either accept or fight against the seal could be very interesting.