The jinchuuriki of Nibi is the central figure. But in the Naruto world, there are many other characters that could be involved. For instance, the Hokage of the village would likely have a role. They might be responsible for the safety of the jinchuuriki and the village, and make decisions regarding the jinchuuriki's training and protection. There could also be other ninja from different clans. Some might be jealous of the jinchuuriki's power, while others might want to form alliances. And don't forget about the Akatsuki. If the fanfiction involves a darker plot, the Akatsuki could be after the Nibi's power and the jinchuuriki would have to fight against them.
I'm not sure specifically as there could be many different 'naruto jinchuuriki of nibi fanfictions'. But generally, it might be about the character who is the jinchuuriki of the Nibi (Two - Tailed Beast) in the Naruto universe. It could explore their powers, their relationship with the beast, and how they fit into the Naruto world's storylines.
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.
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.
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.
It could also include other jinchuuriki from the Naruto universe. For instance, Killer Bee might be a part of it. He has his own unique relationship with his tailed beast and his inclusion could add more depth to the story. Maybe the story focuses on how these three jinchuuriki, Naruto, Gaara, and Killer Bee, interact and support each other while being raised together.
Obviously, Nibi is a main character. And Naruto is often there too. They usually have a strong connection in these fanfics.
Obviously, Naruto is one of the main characters. And the other Jinchuuriki would also be main characters. For example, Gaara, who was the Jinchuuriki of Shukaku. There could also be Killer Bee, the Jinchuuriki of the Eight - Tails. These characters are important as they each have their own unique abilities and personalities.
Maybe Danzo. He's always been a power - hungry character. In a story where Naruto doesn't have the jinchuuriki advantage, Danzo could see it as an opportunity to take over the village without the threat of Naruto's special power standing in his way.
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.