Haren is a central figure. Then there could be a powerful warden who rules the Blood Prison with an iron fist. This warden could be both an antagonist and a complex character with his own motives. There might also be a fellow prisoner who becomes Haren's friend and ally, someone with unique skills or abilities that complement Haren's in their journey through the prison.
Obviously, Haren is one of the main characters. There might also be the prison guards who play significant roles in creating conflict or helping Haren. Another could be a mysterious inmate who has some knowledge about Haren's past or the secrets of the Blood Prison.
Well, a plot idea could involve Haren being framed and sent to the Blood Prison. Once there, he uncovers a conspiracy that reaches outside the prison walls. He then has to find a way to expose it while dealing with the prison's internal power struggles and dangerous inmates. This could involve using his wits and any latent ninja skills he might have.
The main character is Naruto, as it's a Naruto - centered fanfiction. But in the Blood Prison setting, there could be other key characters. For example, the warden of the prison who might be a cruel or mysterious figure. Also, there could be a fellow inmate who has a special connection with Naruto, either as a friend or a rival. These characters play important roles in driving the story forward in the context of the dark and dangerous Blood Prison.
Some fanfictions might also feature the prison guards as main characters. They could be complex characters with their own motives and backstories, and their interactions with Naruto could drive the plot forward. For example, a guard who initially sees Naruto as just another prisoner but then comes to respect him.
Perhaps there is a powerful and mysterious figure lurking in the shadows of the Blood Prison. This character has a vendetta against Naruto and uses the prison's environment and its inmates to try and bring Naruto down.
Naruto himself could be a likely main character. Given his determination and his ability to make friends, it would be interesting to see him in a harem situation within the Blood Prison. He could use his ninja skills to protect the harem members and try to break free from the prison's mysteries.
Naruto is a given as the main character, but Sasuke can also be a popular choice in Naruto Blood Prison fanfiction. Writers might explore the idea of Sasuke ending up in the Blood Prison and how he would interact with Naruto there. Then there's Killer Bee, who could bring his unique fighting style and personality to the prison setting, making him an interesting addition to fan - created stories.
In this fanfiction, Naruto will surely interact with his friends who might be trying to break him out or at least communicate with him from the outside. Inside the prison, he'll encounter inmates with diverse personalities. There could be a wise old prisoner who imparts some valuable wisdom to Naruto. Also, there may be a group of inmates who form a sort of gang within the prison, and Naruto has to either fight them or make peace with them depending on the situation. And of course, there could be a mysterious figure who seems to know more about Naruto's presence in the prison than he himself does, and Naruto will have to figure out this person's motives and identity.
It could be the warden of the Blood Prison. He might be a corrupt figure who is using the prison for his own gain. He sees Naruto as a threat to his operations and tries to keep him locked up at all costs.
It could be one of the powerful and corrupt prison guards. They might have their own hidden agendas and see Naruto as a threat to their power or secrets within the Blood Prison. So, they start a scheme to make it seem like Naruto has betrayed everyone.
The warden of the Blood Prison could be the main antagonist. He might be a power - hungry and corrupt individual who sees Naruto as a threat to his control over the prison. So, he devises plans to get rid of Naruto, which ultimately lead to Naruto's death.