Well, it might start with Naruto being framed for something he didn't do, which leads to the village deciding to leave him in the forest. Once there, he has to use his ninja skills in new and creative ways to find food, water and shelter. He might also encounter some strange creatures or hidden shinobi clans in the forest that change his perspective on his situation.
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.
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.
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.
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.
Well, perhaps Rias, for some reason, abandons Naruto in a dangerous situation where he is left to die. Maybe there's a conflict of interests or a misunderstanding between them. It could be that Rias has to make a tough choice that unfortunately leaves Naruto in a life - threatening state.
One possible plot could be that Naruto discovers a hidden conspiracy within the Forest of Death that led to him being left there. Maybe some rogue ninja or a hidden enemy within the village set him up.
Maybe Naruto is betrayed by someone within the village who sets him up to look like he's dead. Left for dead, he's found by a hermit who teaches him new and powerful jutsu. With his new skills, he plans to return to the village to expose the traitor and prove his worth once again.
In one possibility, Naruto might leave the village to seek greater power on his own. He could feel that the village's teachings and training methods are limited. So, he embarks on a journey across different lands, meeting new shinobi and learning unique jutsu that the village doesn't offer. This could lead to him coming back much stronger, but also with a different perspective on the village and its values.
One possible plot could be that Naruto feels abandoned by Sakura after she chooses Sasuke over him. Naruto then goes on a journey of self - discovery, training harder than ever to prove his worth not just to Sakura but to the whole village. He might face new enemies alone and form unexpected alliances, all while dealing with the emotional pain of being left behind.
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.
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.