Often, the main characters are Naruto and his friends. Naruto, as the protagonist, is naturally drawn to the mystery of the egg. His friends like Shikamaru, who is intelligent and can strategize about how to deal with the situation regarding the egg, and Choji, who might provide some physical protection if needed. Hinata could also be involved, perhaps having a special connection to the egg because of her Byakugan. And then there are the villains, like the members of the Sound Five, who might want to get their hands on the egg for their own evil purposes.
Naruto himself is almost always involved as he is the main character of the Naruto series. His friends like Sasuke and Sakura may also be part of the story. Sometimes, even villains like Orochimaru or Madara could be involved if the plot of the fanfiction is related to a big threat where their knowledge or power is needed.
Obviously, Naruto himself is the central character as it's about him 'snapping'. Sasuke is also often involved. He might be a factor in what causes Naruto to snap, or he could be on the receiving end if Naruto's snapping is directed at his actions or decisions.
In 'naruto angry fanfiction', characters like Hinata can also be involved. If she is in danger or if Naruto feels that he couldn't protect her well enough, it can stir his anger. And villains like Orochimaru or Madara can be present as they are often the source of problems that make Naruto angry, whether it's through attacking the village or harming his friends.
Obviously Naruto himself is the central character as it's about his lifeless eyes. Sakura could also be involved as she is one of Naruto's closest friends. She might be the one to notice the change in his eyes first and try to help him.
Obviously, Naruto himself is the central character. But other characters like Sakura might also be involved. She could be the one trying to get Naruto sober or scolding him for his drunken behavior.
Obviously Naruto himself is the central character as the story is about him cutting himself. Sakura is often involved as well. She is Naruto's friend and a medical ninja. So she might be the one to discover Naruto's self - harm and try to heal him both physically and mentally.
Sometimes Naruto can also be a main character in these fanfictions. He might be the one who notices the neglect of Sasuke's Sharingan and tries to help him in some way. Their friendship could be explored in a new light, with Naruto being more proactive in understanding and supporting Sasuke's power.
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.
In many fanfictions, Kakashi could be involved. As Naruto's former teacher, he has a deep connection with him. He might be the one who discovers some strange things about Naruto's 'death' and starts to look into it further. Hinata is another character that could be important. Her love for Naruto might drive her to not accept his death easily and she could play a part in uncovering the truth.
Obviously, Naruto is the central character as it's about the Kyuubi being released from him. Sasuke also often plays a crucial role. He might be concerned about Naruto's new state, or he could be one of the characters trying to either help or stop Naruto depending on the plot.