The soul power could be related to the Nine - Tails. Since the Nine - Tails is such a powerful entity within Naruto, his soul power might be a way to better control or even transform the Nine - Tails' power in a more positive and spiritual way. For example, instead of just using the Nine - Tails' chakra for brute strength, he could use his soul power to make the Nine - Tails' power more harmonious and less destructive.
Another aspect could be that Naruto's soul power allows him to connect with the souls of his friends and allies on a deeper level. In a dangerous situation, he could use this connection to share his strength or even transfer his soul power to them to help them in battle. This would also emphasize the theme of friendship and unity that is so important in the Naruto series.
One way could be to show Naruto's struggle with the illness while still trying to protect the village. He might have to train his friends to take over his duties in case he gets too sick.
Another way to develop the 'naruto is peaceful' concept is to explore how Naruto deals with internal conflicts within the villages. He could work on improving the social and economic conditions of the lower - class ninjas. By addressing issues like inequality and poverty, Naruto can create a more harmonious and peaceful environment within each village. This, in turn, would contribute to the overall peace in the ninja world. For instance, he could introduce new job opportunities for ninjas who are not good at combat but have other skills like art or cooking.
The concept can be developed by focusing on the visual aspect. Describe how the angel wings look on Naruto. Are they pure white? Do they have a golden glow? Also, think about how they affect his movement. Does he have to learn a new way of fighting?
Another way is for Naruto to inherit an ancient bloodline that enhances his healing power. This bloodline could come with its own set of challenges and secrets that Naruto has to uncover while learning to master the increased power. He might have to face off against those who want to steal this power for themselves.
Well, Sasuke could be the one who notices Naruto's 'in heat' state first. Maybe he sees Naruto's increased passion for training or for protecting the village. He could then either be inspired by it or be a bit worried, which would lead to some interesting interactions between them.
One way could be through Naruto's admiration for Kisuke's unique skills. Maybe Naruto discovers Kisuke's swordsmanship or his knowledge of spiritual energy. He then starts to study Kisuke's ways, trying to incorporate some of his techniques into his own fighting style. This would lead to Naruto changing his combat approach and even his way of thinking about battles.
In a fanfiction, Naruto could be exposed to a new form of chakra or energy similar to Raiden's electricity - based powers. This exposure could lead him to study Raiden's combat style. For example, Raiden's ability to move at high speeds and his proficiency with a sword could inspire Naruto to incorporate new techniques into his own fighting repertoire, thus making him a Raiden fan.
One way could be through a strange crossover event. Maybe Naruto gets sucked into the Bleach universe and is somehow influenced by the power and allure of the Espada. He could start to adapt their fighting styles, for example, learning from their use of reiatsu and zanpakuto - like abilities. This would change his approach to battles in the Naruto world when he eventually returns.
It could be an ancient inheritance. Maybe Naruto is a descendant of a long - forgotten clan that had special soul powers, and these powers have been dormant in his bloodline until now.
To develop this concept further, the fanfiction could show how Naruto's insanity affects his relationships. His friends might start to distance themselves when they sense something wrong, or some might try to help him, which could lead to a lot of emotional and action - filled scenes.