Sasuke could also be a great main character for such a fanfic. Given his complex past and his search for power and revenge at different times, his encounter with the Shinju could be a turning point. He might see the Shinju as a way to gain ultimate power, but then realize there are greater things at stake, like the future of the ninja world and his relationships with his friends.
Naruto himself could be the main character in a Shinju fanfic. He has always been about finding new ways to bring peace and understanding. His connection to the nine - tails could play an interesting role if he were to interact with the Shinju. Maybe he could try to convince the Shinju that the ninja world has changed and it doesn't need to be a source of fear and destruction.
Well, it could be about Naruto obtaining some strange power from eating the Shinju. Maybe he does it by accident in a battle and then has to deal with the unexpected consequences, like new abilities that are hard to control.
Well, one possible consequence could be that he gains some sort of super - power. Since the Shinju is a very powerful and mysterious entity in the Naruto universe, consuming it might endow Naruto with abilities beyond his normal limits. Maybe he could gain control over new types of chakra or even have a better understanding of the origin of all things in the ninja world.
Sasuke Uchiha could be a great choice as the main character. He already has a complex backstory and a lot of room for character development. His journey from seeking revenge to finding his own path in the Naruto series can be further explored in a fanfic.
It could be an original character. Maybe a young ninja who discovers their forging abilities by accident. They might come from a small, unassuming clan that has kept the forging secrets hidden for generations. This character would then have to navigate the Naruto world while keeping their newfound power a secret at first, until they realize they can use it to make a difference.
Perhaps Sasuke could be the main character in a different take on a 'hitman naruto fanfic'. He already has his own vendetta and his skills as a ninja could easily be translated into those of a hitman. He has the Sharingan, which gives him an advantage in combat and tracking, making him a formidable assassin - like figure.
It could be a new character that you create specifically for the fanfic. This character could be an outcast from their village because of their strange Koton abilities. They then have to prove themselves and their powers to the others.
Sasuke could also be a main character in such a fanfic. Given his quest for power and his complex personality, his encounter with the Shinigami could lead to some really interesting character development. He might be tempted by the Shinigami's power or be forced to make difficult choices that would change his path.
Rock Lee could be an excellent main character for such a fanfic. Since he already focuses on physical combat in the form of taijutsu, wushu would be a natural extension for him. He could be sent on a journey to learn the true essence of wushu and bring that knowledge back to Konoha to revolutionize the way they think about physical combat.
Sasuke could be a great main character for a swordsman - themed fanfic. Since he already uses a sword - like weapon, the story could focus on his further development as a swordsman, exploring different sword techniques and their origins.
A new villager who has just moved to the village could be the main character. They are intrigued by the Naruto statue and start to have dreams where Naruto seems to be communicating with them. They then embark on a quest to understand what these dreams mean and how the statue is involved.