Another possibility is that a new character could be introduced as the main character. This character could be a Shinigami - like being who has a connection to the Naruto world. They could bring a fresh perspective and unique abilities to the story, and their interactions with the established Naruto characters would drive the plot forward. For example, this new character could have the power to see the souls of the dead in the Naruto world and use that ability to solve mysteries or prevent disasters.
Sasuke could also be a main character in such a fanfic. Given his quest for power and his complex personality, his encounter with the Shinigami could lead to some really interesting character development. He might be tempted by the Shinigami's power or be forced to make difficult choices that would change his path.
It could be Naruto himself. Imagine Naruto encountering a rogue Shinigami and having to deal with the chaos it brings. He would be the perfect main character as he is always eager to face challenges and protect his friends and the village.
A powerful rogue Shinigami could be the main antagonist. This Shinigami might be jealous of the Shinigami King's power and wants to overthrow him. He sees Naruto as a threat because of his connection to the king and tries to stop Naruto from fulfilling any tasks or missions related to the king. He could also be causing chaos in the living world by releasing dangerous spirits or curses.
I'm sorry I don't know specifically as it's a fanfic. It could potentially feature Naruto himself, or perhaps some other well - known characters like Sasuke or Kakashi. Since it's related to the Shinigami, it might also introduce new characters who are somehow connected to this death - god - like entity.
Since it's a Naruto - related fanfic, Naruto is likely to be one of the main characters. There may also be characters related to the Shinigami, though without reading it, it's hard to say exactly who they could be. Maybe the Shinigami itself could be a major character, or other characters from the Naruto world who get involved in Naruto's encounter with the Shinigami.
Naruto himself could be the main character. Given his adventurous and selfless nature, he might be the one to make the contract to save his friends or the whole Hidden Leaf Village. He would then have to deal with the consequences and powers that come with the contract.
Rukia could be the main character too. As a shinigami, she could be drawn into a strange gaming - like dimension. Her knowledge of the Soul Society and her ice - based zanpakuto powers would be useful in this new and unfamiliar environment. She could also have to deal with her own insecurities and past while trying to navigate through the gaming - inspired challenges.
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.
The two main characters are Naruto and the Shinigami. Naruto, who has reached a god - like state, is now in a relationship with the Shinigami. But we might also see other characters from the Naruto universe. For instance, Kakashi could play a role as Naruto's mentor or friend, giving advice on how to handle his marriage to a non - human entity. And there could be other Shinigami - related characters that are part of the Shinigami's world and interact with Naruto.
The main antagonist could be a corrupted version of the Shinigami itself. The Shinigami that Naruto makes a deal with might be one of the good ones, but there could be an evil counterpart that doesn't want Naruto to succeed. This corrupted Shinigami would use all its powers and minions to stop Naruto from achieving what he set out to do with the deal.
One possible plot could be that Naruto discovers a hidden realm where Shinigami exist. He meets a particular Shinigami and is immediately drawn to their unique powers and personality. They start to form a bond as Naruto tries to understand the Shinigami's world and how it relates to his own.