The villagers of the Hidden Leaf would be divided. Some would be afraid of Naruto, thinking that he's become like the enemy who once attacked their village. Others, who have more faith in Naruto, would believe that there must be a good reason behind his change and would try to support him, while also trying to understand what's really going on. They would be in a state of confusion and unease, not sure whether to trust this new Naruto or not.
Sakura would be worried sick. She'd try to figure out what happened to Naruto to make him act this way. She might try to talk to him, use her medical ninjutsu to check if he's under some kind of genjutsu or has some other problem. She'd be very vocal about her concerns and would try to get the other villagers to help bring Naruto back to his normal self.
The other Konoha ninjas would be quite shocked. The Hokage, whoever it is at that time, would see Naruto's change as a potential threat to the village's stability. They would likely keep a close eye on him and try to figure out what caused this transformation. Meanwhile, the younger generation of ninjas who looked up to Naruto would be confused and disappointed. They expected Naruto to be their role model of a kind - hearted and positive ninja, not someone acting like the feared Madara.
Well, one possible plot could be that Naruto starts to adopt Pain's view on justice. He might see the world as a place full of suffering that needs a radical change. He could begin to question the traditional ways of the Hidden Leaf Village and try to implement some of Pain's ideas in a more positive way, like finding a new system to ensure peace that doesn't rely solely on the power of the ninja villages.
Sasuke would be extremely suspicious. He has always seen Naruto as his rival and a symbol of the village's hope. If Naruto starts acting like Pein, Sasuke would think it's some kind of trick at first. He might even be ready to fight Naruto to figure out what's really going on.
His friends' reactions would be quite diverse. Kakashi, for example, might be intrigued by Naruto's new behavior. He could see potential in Naruto's new - found Kisuke - like qualities. The younger generation of ninja, like Boruto if he were around in this scenario, would look up to this new version of Naruto even more. They'd be inspired by his new cool - headedness and intelligence, while also being a bit in awe of his sudden change in demeanor.
The Akatsuki members, if any are still around, would have diverse reactions. Some might see it as a weakness in Pein, while others might be curious about how this new family dynamic could change the balance of power in the shinobi world. Hinata would be shyly supportive of Sakura. She would understand the importance of love and family, and she would hope that Sakura finds happiness, even if she's a bit intimidated by Pein's past actions.
One possibility could be that Naruto would grow up with a very different view of the world. Pein's ideology of pain and suffering being the means to bring about peace might influence Naruto. He could be more cynical and less trusting, as Pein's methods are quite extreme. Also, his fighting style might incorporate some of Pein's rinnegan - based techniques, having been trained by him from a young age.
If Naruto was an Ajin in a fanfiction, the characters in Naruto would have a mix of reactions. Hinata would be concerned for Naruto's well - being. She might be a bit scared at first because of his new and strange abilities, but still stand by him. The villagers, who have had a rocky relationship with Naruto in the past, might be afraid of him all over again. They could see his Ajin powers as a threat. On the other hand, Naruto's close friends like Shikamaru would try to understand what's going on and help Naruto control his powers if they can.
In a 'naruto acts like gin fanfiction', Naruto might be quieter and more observant. Instead of his usual boisterous self, he could be more like Gin, who is often sly and calculating. Maybe he would have a more subdued way of showing his power and a different approach to his enemies.
Naruto's character would likely become more aggressive. Yujiro is a very aggressive character, and Naruto might start to show similar traits. He could be quicker to anger and more assertive in his actions.
In a fanfiction where Naruto acts like Sesshomaru, the dynamic in the Naruto universe would be completely shaken up. Naruto's relationships would be the most affected. His friends like Sakura and Kakashi would be at a loss as to how to deal with this new Naruto. He would no longer be the one to quickly jump into a fight without thinking. Instead, he would assess the situation more carefully, like Sesshomaru. His appearance might not change much, but his aura would be completely different. He would carry himself with an air of superiority and detachment, which would be a huge contrast to his normal self.