He might become more cynical. Instead of seeing the good in people like he used to, he starts to suspect everyone's motives. For example, he may no longer trust his friends easily.
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.
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.
Maybe he discovers some dark secrets in the Blood Prison. These secrets could be about the corruption of the ninja world or some hidden evils related to powerful people. This new knowledge might make him lose faith in the system he once believed in, leading to his transformation into a darker version of himself.
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.
Might be one of the powerful guards who has a grudge against Naruto for some reason. Maybe he believes Naruto is a threat to the order in the prison and tries to get rid of him secretly.
I haven't read this particular fanfic in detail. But generally, in fanfics about Naruto in the Blood Prison, his changes could involve his growth in power, his relationships with other characters in that unique and often dangerous setting. Maybe he discovers new jutsu or overcomes some inner demons while locked up there.
Another plot could involve Naruto having to deal with a hidden power within the Blood Prison that is starting to corrupt the inmates and guards alike. He has to find the source and stop it. For example, there could be an ancient curse that was placed on the prison long ago and is now awakening. Naruto, with his strong will, tries to resist the curse's influence while also finding a way to break it for everyone else.
Well, in such a fanfic, Naruto's child could be a key element in changing the situation in the Blood Prison. Since Naruto has a child, he might be more determined to break free from the prison's control. The child could also be a target for some evil forces in the prison who want to use the child's potential for their own purposes. And Naruto would do anything to prevent that, leading to intense battles and emotional moments.