Obviously, Naruto will be the main character as the story is about him restarting his life. Sasuke is also likely to be a main character as he was Naruto's rival and friend in the original series. Kakashi too, as he was Naruto's teacher and mentor, will probably play an important role in this new story as well.
The main character is Naruto. However, the Hokage, like Tsunade, could be important in this fanfiction. She was in charge of the village in Naruto's previous life and in his new life, Naruto might interact with her differently. Also, Jiraiya could be a key character. Since he was Naruto's teacher in some aspects in the original, in this new life, Naruto could learn even more from him or use his knowledge of Jiraiya's future to save him or get more help from him.
One interesting plot point could be Naruto having the knowledge from his previous life and using it to train more effectively from the start. For example, he might focus on different jutsu or skills that he overlooked before. Another could be his changed relationships. Maybe he decides to befriend some characters earlier or handle his relationship with Sasuke in a more proactive way in this new life.
Obviously Naruto himself is the central character since the story is about him losing his memories. Sakura would likely be involved too. She's one of Naruto's closest friends and a medic - ninja, so she might try to find a way to restore his memories.
Obviously Naruto would be one of the main characters. He's the protagonist of the original series and his power and will would be crucial in a doomsday scenario. Sasuke would also be likely, as his strength and his connection to Naruto are important elements. Sakura, with her medical skills, would also be a key character as she could be responsible for healing the injured during the doomsday chaos.
Well, it's possible that some new or less - known characters from the Naruto universe could become main characters in 'chaos naruto fanfiction'. For example, Rock Lee could take on a more central role. He has always been a character full of determination and unique fighting style. In a chaotic setting, his strong will could be a key factor in dealing with the chaos. And then there are the jinchuriki of the other tailed beasts who might be more prominently featured as they are all related to the power dynamics in the Naruto world which could be thrown into chaos.
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.
There may be new characters introduced as well. Maybe a mysterious figure who has a special ability to either enhance or dampen Naruto's will to live. This character could add an extra layer of mystery and conflict to the fanfiction.
Naruto would be the central figure. But in this British version, there could be new characters added, like a British wizard - type character who becomes Naruto's mentor in understanding the new 'British - ninja' aspects of his life. And of course, Sasuke and Sakura would be adapted to fit the British setting, perhaps with different family backgrounds that are more in line with British culture.
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.
I think Kakashi would be an important character too. He could be Naruto's mentor in this new situation, teaching him how to use his remaining abilities effectively. Also, Sakura might be there, using her medical ninjutsu skills to try and help Naruto with his crippled state.
The main characters would surely include Naruto himself. His child or children are bound to be in the spotlight. In addition, any of the Akatsuki members who may have reformed or are still causing trouble could be part of the story. For example, if Naruto's child has some connection to the Akatsuki's past actions or secrets, it could bring them into the plot. Also, the villagers of Konoha, who would interact with Naruto's family, could be important characters in this fanfiction.