Naruto is the key character for sure. But there could be new characters introduced in the fanfic as well. Maybe a magical being who helps Naruto understand his powers. And of course, Kakashi could still be an important figure, guiding Naruto in this new journey that combines his ninja training with his magical abilities.
Well, it could be Naruto himself, but with new abilities related to soul magic. He might be the one to discover this new form of magic and use it to protect his village in a different way.
In this fanfic, Naruto is the central figure as the son of Izuna. But characters like Kakashi could still play important roles. He might be the one to guide Naruto in understanding his new heritage. Also, characters from the Uchiha clan, like Itachi, could have different interactions with Naruto. They might be more involved in Naruto's life, either as protectors or as those who want to use his new identity for their own purposes.
Given the title, the central character is likely to be the son of the socceress. However, in a Naruto - inspired fanfic, it's very likely that we'll see Naruto Uzumaki as well. Naruto is such an iconic figure in the Naruto universe that it would be strange not to have him interact with this new character. Also, depending on the plot, other important characters from the Naruto series such as Kakashi Sensei or Jiraiya could also make an appearance.
There could be Sasuke. Since Naruto's situation changes, Sasuke might play a different role in this fanfic, either as an ally or a rival in a new way. Another might be Kakashi. He could be the one guiding Naruto through his discovery of being the son of chaos.
Naruto would likely be one of the main characters. He's the protagonist in the original Naruto series, so it's probable that he'd play a major role in this fanfic as well, especially when it comes to adapting to the god slayer magic.
Perhaps there's a group of magic - wielding ninjas who are either friends or foes. They could have different types of magic, like earth - magic ninjas or wind - magic ninjas. And there might be a powerful sorceress who has a connection to Naruto's family and she could play a key role in his journey to understand his magic.
There could also be new characters introduced, like other Shinigami or beings related to the Shinigami world. For instance, a Shinigami who is Naruto's father figure or a spirit guide who helps Naruto understand his powers. These new characters would add more depth to the story and bring in new conflicts and relationships in the fanfic.
Obviously Naruto himself. And probably some of the Greek gods or goddesses related to Kronos, like Zeus who might be wary of Naruto's existence. Also, Naruto's friends from the original Naruto series like Sasuke and Sakura would still be important as they would be part of Naruto's world and might help him deal with the new situation of being the son of Kronos.
Samul, of course, since he's Naruto's supposed father in this fanfic. He could be a powerful ninja who had some great influence in the past. Another character could be Naruto's mother, who might have a different story now considering her relationship with Samul. Also, characters like Jiraiya could still play an important role. He might be the one to guide Naruto in understanding his new identity as Samul's son and help him train to face the challenges that come with it.
Obviously, the son of Kami would be a main character. And some Shinigamis would also be important. Naruto and his friends could also be main characters as they are part of the Naruto universe. They might interact with the son of Kami and the Shinigamis in different ways.