Sasuke could be a great main character in such a fanfiction. He has a deep connection with Naruto. If Naruto's dying will flame is involved, Sasuke might be on a journey to understand what Naruto left behind and how to carry on his legacy. He could be conflicted between his own past and the new responsibility that comes with the dying will flame.
Another idea is that the dying will flame represents Naruto's unfinished business. In the fanfiction, it could be that there's a threat to the Hidden Leaf Village that Naruto was aware of before his death. His dying will flame then becomes a guiding force for his friends and family to uncover the mystery and save the village. It might lead them to hidden secrets or new allies.
It could be a lone wanderer. This type of character often has a mysterious past and is searching for something in the dying world. They might be drawn to the single flame for reasons they don't fully understand at first.
Well, there could be an old butler who has been in the household for decades. He initially doubts Naruto's abilities but later becomes his mentor. And then there could be a group of thieves who target the wealthy household. Naruto has to use his butler skills and ninja skills to fend them off. And perhaps a childhood friend of Naruto's who visits him at the butler job and is amazed at how he has changed.
Well, obviously his sister would be a main character. She could be someone with a very different personality from Naruto. Maybe she's more introverted and focused on her studies or training in a very solitary way. Another character could be Naruto's mentor, like Iruka. He might be one of the few people who actually notice Naruto's struggle of being ignored because of his sister, and try to encourage Naruto in his own way.
Sakura could be a main character. She could be the one who encourages Naruto to get into dance in the first place. Maybe she has a secret love for dance and wants to share it with Naruto. She could also use her medical ninjutsu knowledge to help prevent dance - related injuries within the group.
Definitely the Kumo ninjas who carry out the kidnapping. There could be some well - known Kumo characters like Killer Bee. He might be involved either directly in the kidnapping (unlikely as he is more of a good guy in the original) or in the events that follow. Another character could be the Raikage. He may or may not be aware of the kidnapping depending on the plot. If he is aware, his actions and decisions would play a major role in how the story unfolds.
Boruto is often a popular character in such fanfiction. Since he also has the Jougan, stories might focus on his training with Naruto to master this power. Their father - son relationship can be explored in new ways as they both deal with the implications of the Jougan.
It's hard to say for sure without reading it, but it could be Naruto himself. Since it's a Naruto - related fanfiction, he might be the central figure dealing with the frozen flame concept.
Sasuke is often a common character. He might be initially suspicious of Female Naruto, thinking she could be a threat to Naruto or the village. But as the story progresses, he could end up being an ally and even help in their adventures.
The nine - tailed fox, Kurama, could also play a major role. Given its long - time connection with Naruto, it may have some influence on Naruto's state of dying or even try to save him in some way. For example, it could share its remaining chakra with Naruto to prolong his life.