If Naruto's black lightning is very powerful, it might make some of his friends worry about his safety. They might try to protect him more, which could change the dynamics of their relationships. Naruto, in turn, might feel a bit smothered by their over - protection, leading to some minor conflicts as they all adjust to this new aspect of his power.
It could strengthen his relationships. His friends might be in awe of his new power and support him more. For example, Sasuke could see Naruto's black lightning as a sign of his growth and respect him even more, leading to a deeper bond between them.
Well, in many fanfictions, Naruto might learn black lightning through intense training. Maybe he gets some special guidance from a powerful shinobi who has mastered it, like Kakashi or some other unknown but strong character. He could also discover some ancient scrolls that contain the secrets of black lightning.
For Naruto's friends like Shikamaru and Choji, they would be quite surprised. Naruto might start to act more like Tobirama in some ways, which could be a bit off - putting at first. He could be more strict or more focused on the long - term goals of the village. This might cause some friction in their friendships until they understand what's going on. With the elders of the village, Naruto could gain more respect as Tobirama was a highly respected figure. But it could also make some of them wary, as they might fear Naruto using Tobirama's knowledge in ways they don't like.
Well, Naruto's relationship with Hinata could be affected in several ways. If Naruto is reincarnated as Kaguya, Hinata might feel a bit distanced from him at first. She would be confused about this new side of Naruto. Also, the other villagers might start to fear Naruto, which could put a strain on his relationship with the whole village. But if Naruto can prove that he's still the same person deep down, he might be able to repair those relationships. His relationship with Kakashi would also change. Kakashi, being a knowledgeable person, would try to guide Naruto through this new development.
His relationship with Sasuke might become more competitive. Sasuke, seeing Naruto learn such a powerful technique, would strive to become stronger too. This could lead to more intense sparring sessions between them and a bit of friendly rivalry.
His relationship with Sasuke could change significantly. With the new power from the merge, Naruto might be seen as more of a threat by Sasuke, or Sasuke could be jealous of Naruto's newfound strength. On the other hand, it could also lead to Sasuke respecting Naruto more and seeing him as an equal in a different way.
As for his relationship with the villagers, some might fear him more because of his connection to Indra. They could see him as a potential threat, like they did in the beginning when they were afraid of the Nine - Tails within him. However, others might see it as a sign of Naruto's importance and start to respect him even more, believing that he is destined for great things because of this reincarnation.
His illiteracy might make his friends initially frustrated. For instance, Sasuke, who is more studious, could be impatient with Naruto's inability to read important messages. But as they grow, they might become more understanding.
With Sasuke, it could either drive a wedge or bring them closer. If Sasuke blames himself for Naruto getting injured while protecting him, he might distance himself out of guilt. On the other hand, it could also make Sasuke realize how much Naruto means to him and he could become more committed to their friendship.
His apathy can strain his relationships. His friends might feel neglected. For instance, Sakura could be confused and hurt as Naruto no longer shows the same eagerness to be part of the team.
In some fanfictions, Naruto might learn to use black lightning through special training with a powerful ninja who has mastered it. Maybe he discovers a new chakra nature within himself that allows him to manifest the black lightning.