Naruto is the main character for sure. Hinata might also be in the fanfic. If Naruto is left to die, Hinata could be one of the few who tries to go against the decision and look for him. There could also be some of the older generation characters like Jiraiya. Even though he might be dead in the original story, in the fanfic he could appear in Naruto's memories or as a spiritual guide to help Naruto when he is in such a desperate situation.
Obviously, Naruto would be one of the main characters. Depending on the specific plot, Sasuke could also be involved. He might be one of the ones who either helps Naruto or is part of the reason Naruto is left to die. Sakura could also play a role, maybe she has a change of heart towards Naruto in the fanfic.
The two main characters are Naruto and Rias. Naruto, with his ninja skills and his journey of growth in his original story. Rias, whose actions towards Naruto are the central focus of this fanfiction. There could be side characters like Naruto's friends from his world who might try to find out what happened to him, or characters related to Rias who could either support or oppose her decision to leave Naruto to die.
Kakashi could also be involved. Maybe he's put in a difficult position where he can't save Naruto for some reason, like being under a powerful genjutsu or being blackmailed. This would create an interesting conflict as he's Naruto's teacher and mentor.
I'm not sure specifically as there could be many different 'naruto is left to die' fanfics with various plots. But generally, it might involve Naruto being in a situation where his comrades abandon him or he is placed in a deadly situation by some malicious force, and then he has to struggle to survive on his own.
Perhaps some of the other ninja villages see Naruto as a potential danger in the future, so they manage to infiltrate Konoha and make it seem like Naruto has committed a great crime, resulting in him being left in the forest. In this case, the main antagonist would be the ninja from the other villages.
In such a fanfic, perhaps Naruto is betrayed by his village and left in the forest. Maybe there are enemies lurking in the forest that he has to face alone. It could also involve Naruto's struggle to survive and his journey to find out why he was abandoned like this.
In some 'naruto left to die fanfic', the plot may revolve around Naruto being betrayed by those he thought were friends. This betrayal could lead to him being stranded in a place where he's left to fend for himself. He may then have to overcome his emotional turmoil and find a way to get revenge or prove his worth.
Sasuke could be a major character. Since Naruto and Sasuke have such a complex relationship, Sasuke might be the one to go after Naruto. Or he could be dealing with his own issues in the Hidden Leaf in Naruto's absence, which could be an interesting sub - plot.
Danzo could be the main villain. He is known for his underhanded tactics and his dislike for Naruto. He might see Naruto as a threat to his power and plan to get rid of him by leaving him in the Forest of Death. Danzo could have manipulated some other characters to make it seem like it was a legitimate mission gone wrong.
Percy is surely one of the main characters, as the story is centered around him being left for dead. There might also be the people who left him, though we don't know who they are yet. Maybe there will be a character who discovers Percy and helps him, like a kind - hearted stranger.
Well, Naruto is the key character as the title implies. However, in fanfictions, authors often introduce new characters as well. There could be a new villain who is constantly trying to kill Naruto but fails every time. And of course, Naruto's friends like Sakura, Kakashi, and Shikamaru might also be main characters. They could be involved in protecting Naruto or helping him out of those life - threatening situations. For example, Sakura might use her medical skills to heal Naruto when he's on the verge of death, and Kakashi could use his wisdom to guide Naruto to avoid death - traps.