In addition to Naruto, there could be his friends like Sasuke or Sakura. They might react to Naruto's newfound ability to sing for demons. Sasuke could be skeptical or jealous, while Sakura might be worried about the potential danger it poses to Naruto. And among the demons, there could be a young demon who befriends Naruto because of his singing, adding an interesting dynamic to the story.
Obviously Naruto would be the main character. He is the one doing the singing. And then there would probably be some demons as well. Maybe a powerful demon lord who is initially intrigued by Naruto's singing and then becomes either an ally or an adversary depending on how the story unfolds.
The main antagonist could be a demon who is threatened by Naruto's singing ability. This demon might be using people's inner demons to gain power, and Naruto's singing that calms those demons is ruining its plans.
It's possible that Kakashi could be a main character as well. His experience and wisdom would be valuable in the face of the threat of the 100 demons. He could be mentoring the younger characters on how to deal with the demons, and his Sharingan might give him some unique insights into the nature of these demonic entities.
Obviously Naruto would be one of the main characters. Since it's about him singing 'We are One'. His friends like Sasuke, Sakura, and Kakashi could also be main characters. They might be either inspired by his singing or play a role in helping Naruto discover this new way of using his voice.
Well, it could be about Naruto using his singing as a way to communicate with demons. Maybe his unique voice has some sort of power over them, like it can soothe the more violent ones or even make them do his bidding.
Obviously, Harry Potter himself would be the main character. He's the one singing the periodic table after all. Then there would be Hermione. She would probably be either helping Harry with the correct pronunciation of the elements or trying to find a logical connection between the magic world and the periodic table. And of course, Ron would be there, making some humorous comments about Harry's singing or being completely confused by the whole Muggle science thing.
There could also be new characters introduced. Maybe a business rival who is jealous of Naruto's success. This rival could be from another village or even an outsider who has his own motives for trying to take down Naruto's billion - dollar empire. And of course, the Hokage would still play a role, as Naruto's actions as a billionaire would have an impact on the village's politics and power structure.
Definitely Naruto himself. He'd be a central character, causing chaos and bringing energy to the daycare. And Sasuke would also be there, probably being a bit of an aloof kid that Naruto is determined to get close to.
Obviously, Naruto would be one of the main characters. Since it's a Naruto - centered fanfiction with the beyonder element added. Sasuke could also be a main character as he is often Naruto's counterpart and rival. They might both be involved in exploring the beyonder powers. Additionally, characters like Kakashi could play important roles. He could be the one guiding Naruto and Sasuke in understanding these new and strange beyonder powers, given his experience and wisdom.
Other Naruto characters like Sasuke or Sakura might also be important. Sasuke could be involved in Naruto's new role as a 'guardian' either as a supporter or a skeptic. Sakura, with her medical skills, could play a role in helping Naruto in his 'guardian' - related adventures, perhaps by healing those affected by new threats that come with the combination of the two universes.
Besides Naruto and Sasuke, Sakura could also be a main character in such fanfiction. Her medical ninjutsu skills might be needed to heal the wounded during the battles against Galactus. And there could be some original characters created specifically for the fanfiction who have some special knowledge or power related to Galactus and the Naruto world.