Obviously, the girl from the whirlpool is the main character. There may also be a mentor figure, like an old wise person who has some knowledge about the whirlpool and can guide the girl on her journey.
There might be a group of friends or allies that the girl gathers along the way. They could be from different backgrounds but are united by their common goal of helping the girl understand and perhaps control the power that comes from the whirlpool.
Often, there's a antagonist. It could be someone who wants to control the power of the whirlpool or someone who is jealous of the girl's connection to it. This antagonist will create obstacles for the girl throughout the story.
The main character is Naruto, no doubt. However, in a 'naruto of the whirlpool fanfiction', there could be antagonists who are also key characters. These could be villains who are after the power of the Uzumaki clan. There might also be side characters like a sensei from the Whirlpool Village who trains Naruto in some unique Uzumaki - related techniques. These characters all contribute to the overall narrative of the fanfiction, whether by helping or hindering Naruto's progress.
In this type of fanfiction, Naruto is a given as a main character. He is the one who gets involved with the story of the Princess of Whirlpool. The princess herself is a major character, with her own backstory, abilities, and goals. Then there could be characters from the Whirlpool Country, like her guards or advisers. These characters help to flesh out the world of the fanfiction and add more depth to the story.
Well, obviously, the 'Naruto prince of whirlpool' is one of the main characters. There might also be his friends and allies from the original Naruto series, like Sasuke or Sakura, who could play important roles in his journey related to his Whirlpool identity.
Obviously Naruto would be one of the main characters. There might also be characters from the Whirlpool like Karin, as she has connections to that place.
Since the content of this fanfic is unknown to me, the main characters could be anyone. It might be a story centered around a heroic character who is unjustly chained to the whirlpool by an evil force. Or it could be a story about a group of characters where one of them gets caught in the whirlpool situation and the others have to work together to save them. There could also be a love interest character who plays a crucial role in the story, either by being a motivation for the chained character to break free or by actively participating in the rescue.
I'm not entirely sure as it depends on the specific fanfiction community. But perhaps there are two main protagonists who are often the center of the love stories, like a charming young man and an intelligent young woman.
One possible main character could be a young ninja from the Whirlpool village who has a special ability related to water manipulation. Another could be a Sand village ninja known for their skill in sand - based jutsu.
Naruto is probably the central figure. And perhaps there will be some supporting characters like Hinata or Sasuke. Also, there could be some long - lost Uzumaki relatives who play important roles as they are likely to be associated with the 'whirlpool' theme in the fanfic.
One possible plot is that the girl is from a family associated with the whirlpool. And she has to break some old family curses or traditions. For example, her family might be bound to a certain area near the whirlpool, and she wants to break free and explore the outside world.
Hinata could be one of the main characters. She might support Naruto in his efforts to rebuild the Whirlpool Village, both morally and with her Byakugan skills which could be useful for scouting and security.