Since I'm not familiar with the exact 'dark shinobi story', I can only guess. There might be a central shinobi character who has some sort of special ability that gets corrupted, leading him to become the 'dark shinobi'. There could also be his comrades or friends who are either trying to save him or are being affected by his actions. And perhaps there's a mastermind behind the events that set the story in motion, manipulating the 'dark shinobi' for their own purposes.
In 'dark shinobi story', there could be a main character who is a shinobi with a troubled past. Maybe there's also a mentor figure who tries to guide him back from the dark path he's on. Another possible main character could be an antagonist, perhaps a powerful shinobi from a rival clan who is involved in the events that push the 'dark shinobi' further into darkness.
In the 'dark release shinobi story', the main character is probably the shinobi possessing the dark release. But other important characters could include the shinobi's family members. For example, a father or mother who has some knowledge about the dark release and its origins in their family. There could also be a love interest, a fellow shinobi who is initially intrigued by the main character's power but later falls in love with the person behind the power. And don't forget about the antagonist, perhaps a powerful shinobi from another clan who sees the main character's dark release as a threat to their own clan's power and supremacy.
Sometimes, characters like Kakashi could also take on a different role in these fanfics. He might be faced with moral dilemmas that are far more complex than in the original series due to the darker nature of the story. And there could be antagonist characters that are original to the fanfic, like a powerful and evil shinobi leader who is trying to reshape the ninja world according to his dark vision.
I don't know for sure, but it could be a young and talented shinobi who is the protagonist.
Perhaps there is a mysterious shinobi who appears out of nowhere and holds the key to the new code. Alongside him or her, there could be a group of shinobi from different clans. They may start off as rivals but as the 'new code shinobi story' progresses, they become allies. Each character would bring their own skills, like stealth, weapon mastery, or special powers related to their clan heritage, to the story.
Well, typically the ashikabi would be a main character. They are the ones with the special power to form bonds with the shinobi. And of course, the shinobi themselves who are bound to the ashikabi would also be important characters. Maybe there's a particularly strong and skilled shinobi who stands out among the rest, like a ninja with extraordinary speed or the ability to use rare jutsu.
I'm not sure specifically without more context, but they could be shinobi with powerful Kekkei Elem abilities. Maybe there's a young, talented shinobi who is just discovering their power.
Since I don't know the specific story, it's difficult to say. But it could be a young and talented shinobi who has the best element kekkei as one of the main characters. Maybe there's also a wise old sensei - type character who helps the young shinobi develop their abilities.
It could be a young and talented shinobi who is on a journey to prove himself in the forest of death. He might be the main character, facing all the challenges bravely.
It could be an older, wiser shinobi who has seen many things in the shinobi world. He might be guiding the younger members of the kekkei clan and be a central figure in the story. There could also be an antagonist, maybe from a rival clan, who is constantly trying to undermine the kekkei clan shinobi's efforts.
Obviously Naruto is one of the main characters since it's in the title. He is likely to be the central focus of the story as the last shinobi.