I can't say for sure without reading it, but I'd assume the snake is a central character. In addition to that, there could be a ninja who discovers the snake in Konoha. This ninja could be an original character created for the fanfic or it could be one of the minor characters from the original Naruto series that gets more focus in this fanfic. And of course, depending on the plot, there could be other characters like the Hokage or other village elders who get involved because of the presence of the snake.
Since it's a fanfic about a snake in Konoha, one main character would likely be the snake itself. There might also be some well - known Konoha ninjas like Naruto, Sasuke or Sakura who interact with the snake in the story.
In the 'a snake in konoha fanfic', the main character is presumably the snake. However, it's likely that there will be other important characters as well. Given the setting in Konoha, it's possible that we'll see some of the main ninja clans' members. For example, members of the Uchiha or Hyuga clans could be involved. They might be intrigued by the snake's presence, or they might be trying to protect Konoha from any potential danger that the snake might bring. There could also be some animal - related characters or summoners in the story who have a special connection to the snake.
I think Naruto is the central character. His friends, such as Kakashi, who was his teacher, would also be main characters. They would be involved in Naruto's journey of dealing with being labeled as a demon in Konoha. Additionally, any villains or antagonists who oppose Naruto because of his 'demon' status could be main characters. For example, if there are some villagers who are against Naruto and try to drive him out, they could be considered main characters in the context of this fanfic.
The main characters are, of course, the Konoha Twelve. This includes Naruto Uzumaki, Sasuke Uchiha, Sakura Haruno, and others. They are the focus of the fanfic and usually the ones driving the story forward with their actions and decisions.
Another main character could be Kakashi. As Naruto's former teacher, he might be conflicted about Naruto's exile. He could be trying to find a way to bring Naruto back to Konoha or at least help him in some way while also having to deal with the village's decision. And of course, there could be new characters introduced specifically for this fanfic, like a mysterious figure who helps Naruto during his exile.
The main characters would most likely start with Naruto. His character would be central to the story. Alongside him, we might see the Hokage at the time also playing a role. Additionally, there could be a group of shinobi who are specialized in dealing with demons that Naruto teams up with. And perhaps some of the villains or demons themselves could be considered main characters in a sense, as they drive the conflict in the story.
I'm not entirely sure as I haven't read this particular fanfic specifically. But generally, in a Konoha - based fanfic with a snake, it might focus on the snake being a unique creature in the ninja world of Konoha. It could be a story about the snake having special powers or abilities that affect the balance in the village. It could also be about the relationships the snake forms with the villagers, either as an ally or a potential threat.
Obviously Naruto is one of the main characters. He is the center of the story as he is the one exiled from Konoha.
Obviously Naruto would be the central character as the title implies his actions towards dooming Konoha. Sasuke could also play a major role. He has his own complex relationship with Konoha and might side with Naruto, or be torn between stopping Naruto and understanding his reasons. Kakashi too could be a main character, as he has a deep connection with Naruto and would likely try to reason with him or oppose him if Naruto is set on dooming Konoha.
Obviously, Naruto would be the main character as it's about his revenge on Konoha. Sasuke could also play a significant role. He has his own issues with the village, and he might either support Naruto's revenge or try to stop him depending on how his character is developed in the fanfic. Sakura might be there too. She could be caught in the middle, trying to figure out whether to side with Naruto or stay loyal to Konoha. And Kakashi, as Naruto's former teacher, would likely be involved. He might be one of the people Naruto has to face if he's set on his revenge, or he could be trying to reason with Naruto.
In addition to Harry, there could be a unique snake character that is a main character. This snake could have its own personality and motives. It might be a magical snake that has been around for a long time and has knowledge of hidden secrets in the wizarding world. Dumbledore could also be a main character as he often guides Harry in the original series and would likely do so in this fanfic as well, especially with Harry's new snake - related situation.
Hermione and Ron might also be main characters in this fanfic. They often accompany Harry on his adventures in the original series, so it's reasonable to think they'd be involved here. They could help Harry figure out the mystery of the snake.