Maybe there is an antagonist in the fanfic, someone who wants to harm the girl or use the snake for their own evil purposes. This could add more drama and conflict to the story, with the girl and the snake having to team up to fight against this bad character.
It could be about a girl who finds herself in a strange situation where she is coiled by a snake. Maybe the snake has some magical powers and is protecting her from an unseen danger.
There could be a brave adventurer who is searching for the girl when she gets coiled by the Titanoboa. He might be an experienced jungle - explorer with knowledge of the local fauna and flora, and he could be the one to try and rescue her from the snake's coils.
The plot might involve the girl being in a prehistoric setting where she encounters the Titanoboa. Maybe she's on an expedition and gets separated from her group. The Titanoboa, being a massive snake, could coil around her out of curiosity or seeing her as a threat. She then has to figure out a way to free herself, perhaps by using her knowledge of the snake's behavior or finding something in the environment to deter it.
The main characters are, obviously, the girl and the snake. The girl is likely a symbol of innocence or perhaps ignorance in the story. And the snake, which is often seen as a symbol of cunning or danger in many stories from different cultures.
Perhaps a wise old snake that has the ability to control the coiling of the other snakes could be one of the main characters. And on the echidna side, a young and curious echidna who discovers a new way to fight the snakes could also be a main character. They would be in the center of the 'echidna wars snake coil' conflict, with their actions and decisions driving the story forward.
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.
Obviously, the main characters are the snake bird and the girl.
It could be an envious sorceress. She sees the girl's beauty or potential power and decides to turn her into a snake girl out of jealousy.
Maybe there's a mysterious figure in the shadows that has some connection to the girl's past. This figure could be an old acquaintance or someone who has a vendetta against her family. Their interactions with the girl would be a major part of the fanfic.
Obviously, the super girl in training would be the main character. There might also be a wise old trainer or mentor who guides her on her journey.