The main characters could include a sensei - type figure who has some knowledge about the 'monster of the leaf' from the past. This sensei could guide the younger characters, both from the original Naruto series and any new ones, in understanding and dealing with the situation. And of course, the 'monster of the leaf' would be at the center of the story, with its own backstory and motives that gradually unfold as the fanfiction progresses.
Since it's a fanfiction, it could have Naruto as one of the main characters. And depending on the plot, there might be a new character who is the demon. Maybe Sasuke could also be involved if the story ties into the existing Naruto - Sasuke dynamic in some way.
Obviously, Naruto would be one of the main characters. Since it's a Naruto - centered fanfic, he's likely to be at the core of the story. There might also be his friends like Sasuke and Sakura. They could play important roles in how they deal with Naruto's'monster' transformation or whatever the story has in store for him.
It's hard to say for sure without reading it. But it could be some well - known Naruto characters like Zabuza or Kisame who are from Kiri and might have a connection to the monster. Maybe there are also some original characters created specifically for this fanfiction.
Sasuke could also be a main character. His Sharingan abilities could play a role in detecting or fighting the chakra monsters. Maybe he teams up with Naruto again to deal with this new threat.
Obviously Naruto would be one of the main characters as the story is about getting him back. Sakura could also be a main character. She might be one of the ones leading the effort to bring Naruto back, using her medical skills and her friendship with Naruto as reasons to convince him.
Typically, there would be a young and ambitious trainer as one of the main characters. They are on a journey to become the best in the Burning Leaf region.
Obviously, Naruto himself is always a popular character. His determination and growth throughout the story are always interesting to explore further in fanfiction.
Obviously, Naruto would be one of the main characters as he is from the Leaf Village and would likely lead the charge against the agents of Mist. Sasuke could also be there, as he often teams up with Naruto in important battles. Sakura might be involved too, using her medical and combat skills. And from the Mist side, there could be some important ninja agents who are the antagonists, though their identities would be developed as the story progresses.
Obviously, Naruto would be one of the main characters. And from Monster Musume, characters like Miia could be important. Miia is one of the more prominent characters in Monster Musume, and her relationship with Naruto could be explored. Maybe she could be like a mentor or a friend to him, helping him understand the Monster Musume world better.
Perhaps a plot where the 'monster of the leaf' is actually a misunderstood being. It could start as an outcast but then as the story unfolds, it turns out to be a key figure in saving the leaf village from a great threat. Maybe it has some hidden knowledge or power that only gets revealed in the most crucial moments.