An orphan with no known family could be the main character. They discover they have a hidden bloodline through a series of events. It could be a bloodline that gives them the ability to see the past or future in dreams. This character would then be on a journey to figure out where they came from and what their power means, all while trying to fit into the ninja society.
Another option could be a relative of an existing character. Maybe a long - lost cousin of Sasuke who has the Bakuton bloodline. This would add an interesting dynamic to the existing relationships in the Naruto story. They could initially be on a different path, but through the power of the Bakuton bloodline, their path crosses with the main characters.
Sasuke could also be a great main character for this kind of fanfiction. With his already complex character arc in the original series, adding the kami bloodline to his story could take it in new and exciting directions. He could struggle with the power of the bloodline, perhaps fearing it would make him too much like those he has fought against in the past, or he could use it to seek revenge in a more powerful way than before.
It could be Sasuke. He already has a thirst for power and a complex backstory. Discovering an Espada bloodline would add another layer to his character. He could use the new powers to seek revenge in a more powerful way or perhaps find a new purpose in protecting the village instead of just avenging his clan.
It could be an original character created specifically for the fanfiction. This new character could be an outcast in the Naruto world because of their bloodline, and the story could revolve around their journey to find a place where they are accepted.
Maybe an existing minor character from the Naruto series who is revealed to have the insect bloodline. For instance, that one student in Naruto's class who was always quiet and unassuming. As the story unfolds, we find out they have this amazing bloodline ability with insects and they start to develop it and become a key figure in the village's defense.
It could be a rogue ninja from a forgotten clan who is jealous of Naruto's new - found power from his hidden bloodline. This antagonist might try to steal Naruto's bloodline ability for himself.
Samui could be a great main character. She is a strong and intelligent kunoichi from the Hidden Cloud. Her skills in combat and her calm demeanor would make for an interesting story as she takes on various challenges within the village and outside.
It could be an original character created by the fanfiction writer. This character could be from a minor clan in the Naruto universe but has extraordinary intelligence and potential.
I think Naruto himself would be an amazing character with the gravity bloodline. Imagine him combining his existing Rasengan with the power of gravity. He could create a Rasengan that not only spins but also has a crushing gravitational force. Also, Naruto's never - give - up attitude would be perfect for mastering the complex abilities that come with this bloodline. He would constantly push himself to find new ways to use it in battle and for the good of the village.
Sasuke could be a great candidate. He has always been a bit of an enigma, with his brooding nature. He could be hiding a new power or a different side of his personality behind a mask, either self - imposed or as a result of some outside influence. Maybe he's trying to hide his true intentions from Naruto and the others as he pursues his own goals.