The jailer and an old, wise shinobi could be the main characters. The old shinobi used to be a great hero but now is retired. He sees the same potential in the jailer that he once had. He mentors the jailer, teaching him old techniques that were forgotten. Together, they face a new threat to the village that the other shinobi are ill - equipped to handle.
Well, it could be about a jailer in the Naruto universe who is constantly overlooked and underestimated. Maybe he has some unique skills or knowledge that no one pays attention to. And as the story unfolds, he starts to prove his worth in unexpected ways, perhaps by saving the village from a hidden threat that the regular shinobi missed.
It could be that some of the neglected characters from Naruto, like Rock Lee for instance, are made main characters in this fanfiction and are paired with a Gremory character. Maybe a Gremory character who also has been somewhat overlooked in their own series. This would give a new perspective and new storylines to explore.
I'm not sure specifically as it's a fanfiction and can vary greatly. But it could potentially have Naruto characters like Naruto himself or Sasuke, combined with some Tokyo Ghoul characters like Kaneki. Maybe there are also some original characters created for this fanfiction.
Obviously, Naruto is one of the main characters. Since it's related to him being involved with a neglected god. The neglected god itself is also a main character, as the whole story revolves around its relationship with Naruto. There might also be other characters like Sasuke or Sakura who could be involved in different ways. For example, Sasuke might be suspicious of Naruto's newfound connection with this god and it could cause some tension between them.
Sasuke could be one of the main characters. He might be initially suspicious of the neglected emperor, thinking he could be a threat to the balance of power. But as the story progresses, he could come to understand the emperor's situation. Another character could be Kakashi. He would likely be the voice of reason, trying to analyze the situation objectively and guide Naruto and the others in dealing with the emperor.
A potential main character could be a long - lost relative of Hashirama who has the mokuton ability but has been neglected in the main Naruto story. This character could then embark on a journey to discover their true power and place in the ninja world.
Obviously Naruto himself would be a main character. He's the focus of the 'neglected' aspect and the 'king' idea probably revolves around him. Sasuke might also be a significant character. His relationship with Naruto could be very different from the original. Since Naruto is neglected, Sasuke might be in a more powerful position within the village, which could create a lot of tension between them.
Another option for the main characters could be Kaiba from Yugioh. His pride and determination would make for an interesting dynamic when faced with the neglect from the Naruto world. And from Naruto, Sasuke could be involved. He might initially see the Yugioh characters as a distraction from his own goals, but later on, things could change.
The obvious main character would be the neglected Anbu prodigy. He could be someone with a tragic past that led him to the Anbu in the first place. Another important character could be Naruto himself. Even though it's about the neglected prodigy, Naruto's presence is what causes the neglect, so he would play a significant role in the story.
Obviously Naruto is one of the main characters. And then usually some of the female characters like Sakura, Hinata, and Ino are often part of the harem that is being neglected. They are the ones who would typically have some sort of romantic feelings for Naruto in these fanfictions.