There could be some old and wise ninja masters. These are the ones who have studied ancient sealing techniques for years. They guide the younger generation of ninja in the fanfiction and use their wisdom and experience to plan and execute the sealing of Madara. Their role is like that of a strategist, ensuring everything goes smoothly.
Often, the main character or the protagonist is involved. They might have some special powers or knowledge that enables them to take part in the sealing. For example, if the protagonist has a unique kekkei genkai that can nullify Madara's abilities to some extent, they would be crucial in the sealing process.
Naruto is often paired with Madara in some fanfictions. Their interactions can be really intense, as Naruto tries to either convince Madara to change his ways or fight against his reborn form.
It can completely change the power balance. With two of the most powerful ninjas sealed, new characters may rise to fill the power vacuum. This could lead to new rivalries and alliances.
There might be an original character in the fanfiction who is a sealing expert. This character could be on a quest to find the Scroll of Sealing to complete their collection of rare sealing knowledge. Along the way, they might encounter Naruto and his friends, and together they face the challenges related to the scroll.
Typically, the main character would be the prodigy in sealing. However, there could also be other important characters such as their friends or rivals. Their friends might support them in their journey to master sealing, while their rivals could be other ninjas who are jealous of their talent or who have different ideas about how to use sealing techniques. There might also be villains who try to take advantage of the prodigy's skills for their own evil plans.
Sasuke could be a main character as well. Given his own experiences of being an outcast and having a thirst for power at times, he could relate to Madara in some ways. They might form an unexpected alliance or have a rivalry based on their shared experiences of feeling neglected or misunderstood in the ninja world.
Sasuke is often a popular character in these fanfictions. He might play a role in helping Naruto against Madara or have his own motives during their battle. Kakashi can also be a prominent figure, perhaps using his Sharingan in a crucial moment to assist Naruto. Another popular character could be Hashirama, as his connection to Madara is a key part of the original story and can be further explored in fanfiction.
Obviously, the heir of Madara would be a main character. There might also be other characters from the original Naruto series, like Naruto himself. Naruto could be in opposition to the heir, seeing them as a threat to the peace he has worked so hard to achieve.
Obviously, Madara himself is a main character. He is the center of the story's legacy aspect. Naruto might also be a main character as he often represents the new generation and the hope for change in the Naruto universe. He could be the one to either oppose or understand Madara's legacy in the fanfiction.
Definitely Naruto. And among the Nara clan, Shikamaru is a must - have. He's intelligent and has a unique relationship with Naruto. Besides, Shikamaru's mother could be a character. She could be the one who takes care of Naruto in a more motherly way, showing him the warmth of a family. Also, the clan elders might be involved. They would have to make decisions regarding Naruto's adoption and his place within the clan.
Naruto himself could still be a main character. His relationship with Madara's reincarnation could be explored, like how he tries to understand this new version of an old enemy and whether he can trust him or not.