The main antagonist could be a rogue ninja who has infiltrated the village's council. This ninja could be secretly manipulating things behind the scenes to get Naruto sent to prison. He might have a vendetta against Naruto for some past encounter or just see him as a threat to his own evil plans.
It could be that Naruto is sent to prison as part of a political move. There are some ninja clans within the village who are jealous of his popularity and influence. They conspire to get him out of the way by making it seem like he's a threat to the village's security. In prison, Naruto discovers a hidden conspiracy within the prison walls that is related to the outside political turmoil and he has to find a way to expose it while also getting himself released.
He could use his transformation jutsu. He could transform into a guard or an inmate who has access to the prison exit areas. Then he could just walk out when the opportunity arises.
Well, one possibility could be that Naruto is framed for a crime he didn't commit and sent to the Blood Prison. There, he might face all kinds of dangerous inmates and tough prison guards. He would probably try to prove his innocence while also having to deal with the harsh prison environment and maybe some secret plots within the prison walls.
" Summoning Souls " was an ancient novel written by Shan Zhizi. The story was about Xu Hexue's sins and Ni Su's encounter with him. Xu Hexue had been dead for fifteen years, but there were still people talking about his evil deeds in the streets of Da Qi. During Ni Su's most difficult times, she only had Xu Hexue by her side. Together, they searched for Ni Su's elder brother and sought justice. When Ni Su was about to marry an outstanding suitor, she parted ways with Xu Hexue. This novel might interest you.
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.
One possible plot twist could be that Naruto discovers a hidden conspiracy within the Blood Prison. Maybe the prison is being used for something more sinister than just holding criminals. Another twist could be that Naruto's friends believe he's a traitor for ending up in such a place and he has to prove his innocence to them while still trapped in the prison.
In fanfiction, if Naruto gets sent to Blood Prison, he might face a lot of challenges. He could encounter powerful and dangerous inmates. Naruto would probably try to use his ninja skills and his strong will to survive. Maybe he'd also find some allies among the prisoners who recognize his strength and good heart.
In this situation, Naruto could also use his ninja skills in a discreet way. For example, he could use his shadow clone jutsu to gather information without being noticed. He might discover that the ones who framed him are actually part of a larger conspiracy against the Hidden Leaf Village. So, his main goal would then not only be to get out of prison but also to expose this conspiracy.
There are indeed alternatives. Some fanfics might explore the relationships between Naruto and other characters in the Blood Prison context. For example, they could depict how Naruto interacts with the guards or other prisoners in a way that promotes the values of the Naruto universe, such as perseverance, loyalty, and friendship. It's important to avoid the offensive ones and seek out the positive fan - created stories.