Since it's a Naruto - based fanfiction, Naruto is likely to be one of the main characters as he is the Jinchuuriki. There might also be other characters from the Naruto universe such as his friends like Sasuke, Sakura, etc. who could be involved in the story related to Naruto's connection with the Shinigami.
Well, the main character is surely Naruto given that he is the Jinchuuriki of the Shinigami in this fanfiction. However, other characters could also be central to the story. For instance, Jiraiya could be involved. Jiraiya was Naruto's teacher and had a deep understanding of many things in the Naruto world. He could offer guidance to Naruto regarding his connection to the Shinigami. Additionally, villains from the Naruto series might also play a part. They could be interested in Naruto's new connection and try to either use it for their own gain or try to destroy it, which would bring about conflict and further the plot.
I'm not sure specifically as there could be many different plots in such a fanfiction. Generally, it might involve the Naruto character who is a Jinchuuriki (a host of a tailed beast) having some sort of connection or interaction with the Shinigami (the god of death in some contexts). It could be about how his Jinchuuriki powers are affected by this connection, or perhaps adventures that come from it.
Some fanfictions might also introduce new or less - known Jinchuuriki characters. They could be from different hidden villages or have special backstories. These characters add more variety to the story and can bring new dynamics to the relationships between Naruto and the other Jinchuuriki. Their inclusion can also expand on the lore of the Jinchuuriki in the Naruto universe.
Obviously, Naruto would be one of the main characters since he is the leader. And the jinchuuriki would also be main characters, like Gaara who is the jinchuuriki of Shukaku.
Obviously, Naruto would be one of the main characters since it's in the title. And the Shinigami who gives the gift is likely to be another important character.
Naruto is surely the central character in this fanfiction. Given the title, the Shinigami is another key figure. It's possible that characters like Kakashi could also play important roles. Maybe he serves as a mentor to Naruto in understanding the powers and responsibilities that come with being the champion of the shinigami. Also, villains or antagonists related to the shinigami's realm might be introduced as main characters to oppose Naruto.
Obviously Naruto would be one of the main characters, as the title implies he is the son of the Shinigami. There might also be other Naruto -verse characters like Sasuke, Sakura, and Kakashi who could play important roles. Maybe the Shinigami itself might be a character in some form, either as a physical presence or a guiding force in Naruto's life.
Apart from Naruto and the Shinigami, there could be other characters from the Naruto universe. For example, Sasuke might be involved. He could be either jealous of Naruto's new blessing or he could end up being an ally in Naruto's journey with this new power. Also, Kakashi could be there to guide Naruto in understanding and using the power given by the Shinigami. Maybe there are also some original characters created specifically for this fanfiction that are related to the Shinigami's realm or have some connection to Naruto's new situation.
Obviously Naruto would be one of the main characters since the title implies he is the substitute shinigami. There might also be other characters from the Naruto universe, like Sasuke or Sakura, who could be involved in Naruto's new role. They might either support him or be skeptical of his newfound powers and responsibilities.
Obviously, Naruto is one of the main characters. And of course, the Shinigami King. There may also be other characters from the Naruto series who interact with Naruto in the context of his relationship with the Shinigami King, like Sasuke or Kakashi.
The Jinchuuriki's mentors or those who protect them could also be main characters. For instance, Kakashi could be a main character in a fanfiction where he is tasked with training a new Jinchuuriki. His experience and wisdom would play a crucial role in the Jinchuuriki's development, and his interactions with the other characters in the village would add depth to the story.