Well, Harry is for sure the central character as it's his rebirth that's the focus. In addition to him, there could be his friends from the original story, if they also get involved in his new adventure in the sky world. There might also be some sort of sky deities or powerful entities that serve as antagonists or mentors in this fanfiction. These new characters would add more depth and intrigue to the story.
Since it's about Harry being reborn in a sky - related world, Harry is the main character. However, depending on the direction the author takes, other characters could be introduced. For instance, if the sky world has a society, there could be leaders or outcasts within that society that Harry interacts with. Maybe there are characters who have a special connection to the sky, like those who can communicate with sky spirits. All these potential characters can create a rich and diverse cast for the fanfiction.
Obviously, Harry as the reborn Black would be a main character. Sirius Black would probably also play a major role, as he's an important part of the Black family. And Bellatrix Lestrange could be another key character, her relationship with the Black family and her own dark nature would create a lot of interesting interactions with Harry in his new identity.
Obviously, Petunia in the form of reborn Harry would be the main character. Vernon and Dudley Dursley would also be important as they are part of the family. And we can't forget about the wizarding world characters like Dumbledore. He would surely notice some changes in Petunia and might start to investigate. Also, there's a good chance that Hagrid would be involved in some way, perhaps bringing some news or event that would set the story in motion for Petunia!Harry.
Obviously, Fem Harry would be the main character. There could also be characters inspired by Skyrim, like the Dragonborn or various NPCs that Fem Harry interacts with, such as shopkeepers or guild masters.
Obviously, Deku would be the main character since it's about being reborn as him. But other characters like All Might are also likely to be important. All Might was a huge influence on Deku in the original story, and in the fanfiction, he could still play a crucial role in mentoring the reborn Deku.
Neville could be another character. He might look up to Harry even more in his dragon form, seeing him as an even more powerful protector. Hagrid would be excited to have a dragon - Harry around. He could help Harry understand his new dragon nature. And some of the Slytherins, like Draco, might be jealous or scared of Harry's new form.
Since I don't have specific information about this fanfiction, I can't say for sure who the main characters are. But they are likely to be the original characters (OCs) created for the 'Reborn's Sky' universe.
Obviously, Harry would be the main character. Since it's about him being a Saiyan. And I think some of his friends from the Harry Potter series might also be important characters, like Hermione and Ron. They could react to Harry's new Saiyan identity in different ways.
Obviously, Harry would be the main character as the title implies. But other characters like Hermione and Ron would also be important. They could either be part of Harry's regime, reluctantly or wholeheartedly, or they could be part of the resistance against his dictatorship.
Obviously, Harry would be the main character. Since it's about him being a playboy, he would be at the center of the story. There might also be his friends like Ron and Hermione. They could play important roles in either supporting or trying to change Harry's playboy ways.
Hermione and Ron are also likely to be important characters. They would be there to support Harry, try to figure out what's going on, and probably try to save Harry from this dangerous situation. Hermione with her vast knowledge of magic might be trying to find a way to break the connection between Harry and Voldemort, while Ron would be there with his loyalty and courage to stand by Harry.