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 wrongly accused of a crime in the Hidden Leaf Village and is sent to prison. There, he might meet other prisoners with unique abilities or stories. He could use his ninja skills in a different way, like trying to maintain peace among the inmates. Maybe he'd also be planning his escape while uncovering the real truth behind his false accusation.
One common theme is redemption. For example, a character who has made mistakes in the Naruto world might be sent to the prison school to atone and grow. Another theme is survival. The prison school environment is often harsh, so characters need to find ways to endure.
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.
One common theme is the unjust imprisonment of Naruto. Usually, it's due to some false accusations or political machinations in the Hidden Leaf Village. Another theme is the use of unique jutsus or skills for the break. For example, Naruto might use his Nine - Tails chakra in a new way.
In a 'naruto goes to prison' fanfiction, it could be that Naruto is tricked into taking the blame for someone else. Once in prison, he meets old foes who are also incarcerated. Instead of fighting them, he tries to understand their motives and in the process, he uncovers secrets about their pasts that were related to some greater threat to the ninja world. This knowledge then becomes crucial for his future actions outside the prison.
It could be a corrupt ninja from within the village who wants Naruto out of the way. Maybe someone jealous of Naruto's popularity and power, so they frame him and get him sent to prison. This antagonist would then try to keep Naruto in prison by any means necessary.
In this type of fanfiction, the plot can be really diverse. It might start with Naruto being sent to the Blood Prison for some false accusations. Once there, he encounters various characters, some of whom are trying to kill him, while others might become his allies. The Blood Prison setting allows for a lot of exploration of Naruto's character in a darker context. It could also involve Naruto having to use his skills in new and creative ways to survive, and perhaps there's a build - up to a big showdown against the main villain or the corrupt forces running the prison.
In Naruto prison harem fanfiction, Orochimaru could be a character. His devious and powerful nature can create a lot of conflict and drama in the prison setting. Hinata might also be present, with her shy but strong - willed personality being an interesting contrast to the other more assertive characters. And of course, Shikamaru, with his intelligence, can play an important role in the various plots and relationship developments within the prison.
One possible plot could be that the prison warden has to deal with powerful ninja prisoners who are constantly trying to escape. Maybe some of them are rogue ninjas with unique abilities that the warden has to figure out how to contain. For example, a prisoner who can turn invisible or teleport within the prison. The warden would have to use his or her own ninja skills and intelligence to keep the prison in order.