Naruto is sure to be a main character. In addition to him, there could be a mysterious figure who is the keeper or the source of the dragon of darkness. This character could be both a threat and a potential ally. Naruto's sensei, Kakashi, might also play a role as he often guides Naruto. And there could be a group of shinobi from another village who are also interested in the dragon of darkness, either for good or bad reasons. Their interactions with Naruto and his friends would add more depth and complexity to the story.
Since I haven't read it, it's hard to say for sure. But it could be Naruto himself as he is the main character in the original series. There might also be an original character created for this fanfiction who has a connection to the dragon of the darkness flame.
Obviously, Naruto is a main character in these fanfictions. He's usually the one who gets the red eyes and the connection to the Darkness Dragon. Sasuke might also be involved, either as a rival who is intrigued by Naruto's new power or as a partner in exploring the secrets of the red eyes. Sakura could be there as well, perhaps trying to help Naruto control the power so it doesn't consume him. And sometimes, characters from other clans or villages might make an appearance, like Gaara, who might be interested in the power because of its potential threat or its possible use in protecting his own village.
Well, Naruto is surely a main character. And depending on the plot, characters like Kakashi could be important. He's Naruto's teacher and might try to guide Naruto away from the allure of darkness. Also, Orochimaru could be a key figure. He's always been associated with dark arts in the Naruto series, and in this fanfiction, he might play a role in Naruto's exploration of the darkness, either as an ally or an enemy.
The main characters would surely include Naruto. Then, depending on the direction of the fanfiction, characters like Jiraiya could be important as he might be the one to help Naruto understand and control his dark side. There could also be some dark - themed characters that are part of Naruto's heritage or the source of his 'son of darkness' status. And of course, his friends, even if they are initially wary of him, would still be key characters as they react to Naruto's transformation or discovery of his new identity.
Most likely Naruto would be one of the main characters. Depending on the crossover, it could also include characters from the other franchise involved in the crossover.
Obviously Naruto would be one of the main characters as he is the 'King of Darkness' in this fanfiction. Sasuke could also be a main character as his relationship with Naruto is so central in the original series and would likely be explored in a new way in this dark version. Sakura might also be a main character as she may try to bring Naruto back from the dark side.
Well, Naruto would be the main character for sure, since it's about him as the god of darkness. Sakura and Sasuke could also be important characters. They might be trying to understand Naruto's new form and powers, and either help him or be in conflict with him depending on how the story goes.
In addition to the usual Naruto characters, there could be some original characters created specifically for this fanfiction. Maybe there's a mysterious figure who is either guiding Naruto towards the darkness or trying to stop him from fully succumbing to it. Another possibility is that some minor characters from the original Naruto series get more spotlight in this fanfiction and play important roles in the story related to Naruto's 'bringer of darkness' arc.
Well, it could be an original character created specifically for the fanfiction. This character might be an outcast because of their Darkness Release abilities. Maybe they are trying to prove themselves in a world that fears their power.
Most likely Naruto would still be a main character. He is the protagonist of the original series and would probably be central in this fanfiction too, as he battles against the darkness. Sasuke could also be a main character, especially if the story is about his struggle with his own dark side or his relationship with Naruto in this darker context.