Rock Lee could be a really unexpected but fun main character. He's always looking for challenges, and getting involved with a crime boss could be the ultimate test for him. He could be trying to reform the crime boss with his positive attitude and unwavering ninja way, or he could be tricked into working for the crime boss at first and then has to find a way out.
Sasuke could be a great choice. He has that brooding, anti - hero vibe that could fit well in the criminal underworld. Maybe he gets drawn into the crime boss's schemes because he thinks it's a way to gain more power to achieve his own goals.
Sakura could be a main character. She is a skilled medic - ninja. So, she might be involved in trying to figure out why the flowers are wilting. Maybe she thinks it's related to some new disease in the plant life of the Naruto world and she uses her medical knowledge to investigate.
Sakura could be a great main character. You could show her growth during the bell test, not just as a ninja in terms of skills, but also in her self - confidence. Maybe she has to take the lead when Naruto and Sasuke are incapacitated for some reason.
Sakura could be one. She has a long - standing relationship with Naruto and might be part of the harem. Also, Hinata. Given her feelings for Naruto, she could be drawn into this situation. Shikamaru might also be included, not in a romantic way for Naruto but as a friend who gets involved in the group dynamic. And Kiba, with his brash personality, could add an interesting element to the group.
Perhaps there's a group of magic - wielding ninjas who are either friends or foes. They could have different types of magic, like earth - magic ninjas or wind - magic ninjas. And there might be a powerful sorceress who has a connection to Naruto's family and she could play a key role in his journey to understand his magic.
Kakashi could also be a main character. He has lost many people close to him, like his father, Obito, and Rin. Facing the death goddess, he could be in a moral dilemma. He might be tempted to use her power to change the past, but also realizes the consequences that could come with meddling with death. His internal struggle could be a central part of the fanfiction.
It could be Sakura. In the original Naruto series, she had feelings for Sasuke for a long time. But in this fanfiction, she could shift her attention to Naruto and be the one who wants him to be hers. Maybe after seeing Naruto's selfless acts and his growth, she realizes that he's the one she should be with.
It could be an old veteran ninja who, after years of service, decided to open a shop. He has a gruff exterior but a heart of gold. He uses his war stories to attract customers, especially the young ninja trainees who are eager to hear tales from the front lines while they browse his selection of kunai and shuriken.
Hinata could be an idol trainee. She is shy at first but as she trains, she becomes more confident. Naruto could be her biggest supporter, and their relationship could develop further as they both pursue their dreams in the idol and ninja worlds respectively.
There could be members of the Gremory family. For example, Rias Gremory might be a key character. She could be one of those who initially neglect Naruto but later come to realize his potential. Another character could be Issei Hyodo, who might be in a position where he has to choose between the traditional Gremory way and Naruto's different approach.
Sasuke could be a great love interest. He has a complex personality with his dark past and his journey of redemption. A fanfic could explore a relationship where the protagonist helps Sasuke fully come to terms with his past and in the process, they fall in love. His cool and aloof exterior would make for an interesting dynamic as the relationship develops.