His character might develop a sense of distrust towards the system that put him in the Blood Prison unjustly. He could become more cynical at first but then use that as motivation to change the ninja world for the better.
He may develop a deeper understanding of the darker side of the ninja world. This new knowledge could make him more empathetic towards those who have been wronged or marginalized. He could start to work towards creating a more inclusive and just ninja world, not just for Konoha but for all villages.
Naruto could become more resourceful. After being in such a harsh environment like the Blood Prison, he might have learned new ways to survive and escape difficult situations. This would make him more confident in his abilities and more willing to take risks in future missions.
Naruto's character would likely become more protective. He has always been about protecting his friends and the village, but now with a child, his sense of responsibility would grow exponentially. He would be more cautious in his actions in the Blood Prison as he doesn't want to put his child in danger.
Naruto may also develop a darker side to his personality. The abandonment could make him feel betrayed and angry. He might struggle with controlling his emotions, especially his anger. However, this could also lead to him learning how to channel that anger into power in a more controlled manner, like he did with the Nine - Tails' chakra, but in a more refined way.
One interesting plot twist could be that Naruto discovers a hidden power within the Blood Prison that he can use to his advantage outside. For example, he might gain the ability to sense the true intentions of people, which would make him even more perceptive in his future battles and interactions.
His character may become more independent. Without relying on his family, he has to fend for himself and make his own decisions. This can lead to him being more self - assured. For example, he might be quicker to take risks in battles or in making important choices.
Naruto may become more self - reliant. Without the support of his parents, he has to figure things out on his own. He might grow up faster, learning to take care of himself at an early age. For example, he would have to learn how to cook, clean, and do other basic life tasks all by himself.
He might become more withdrawn. Without his happiness, Naruto would lose his usual exuberance. He would probably start to isolate himself from others, as he no longer has that positive energy to share. For example, he might stop going to his favorite ramen place and avoid his friends.
Naruto's development could involve him becoming a more calculating shinobi. In ANBU, he has to think several steps ahead. His fighting style might change from his usual straightforward attacks to more strategic and stealthy ones. He would also have to suppress his emotions more, which could lead to some internal turmoil as he struggles to keep his true self hidden.
Naruto's character development in this fanfiction might involve him becoming more of a leader. With his new skills from training, he can inspire others and lead by example. He may also be more patient, having learned the value of hard work and perseverance during his training.
One possible plot could be that Naruto was wrongly imprisoned. After being released, he has to prove his innocence while also dealing with the changed perception of him in the village. He might go on a journey to find out who framed him and along the way regain the trust of his friends and the villagers.
He would become more reliant on his friends and allies. Since he doesn't have chakra to fall back on, he has to trust others more and learn to work in a team in a different way.