His friends would be horrified. Sasuke, for instance, who has known Naruto for a long time, would be shocked at this transformation. He might initially try to reason with Naruto, thinking that there's still some good left in him. But as Naruto's psychopathic behavior continues, Sasuke would be forced to consider him an enemy and take action to stop him if necessary.
His enemies would also be taken aback. They are used to Naruto being the heroic type. But now, if he becomes a psychopath, they might be confused at first. Some might see it as an opportunity to use him for their own evil purposes, while others might be too scared to approach him, fearing that his unpredictable and violent nature could turn on them at any moment.
Sasuke would be deeply affected. He would probably feel guilty for not being there to save Naruto. At the same time, he would vow to uphold Naruto's ideals and make the ninja world a better place, as a way to honor his friend's sacrifice.
Sasuke would be very conflicted. On one hand, he has his own goals, but on the other, Naruto is his friend. He might initially try to fight Naruto to stop him from doing harm, but then he would focus on finding a way to break the brainwashing.
Sakura would be heartbroken. She's always had feelings for Naruto, and seeing him insane would be a huge shock. She'd likely try to use her medical skills to find a cure for whatever is ailing Naruto's mind. She might also try to get help from Tsunade, hoping that the former Hokage's knowledge could save Naruto.
Sasuke would probably be both confused and a bit disgusted at first. He might see Naruto's new form as a sign of weakness. Sakura, on the other hand, would likely be more sympathetic and try to find a way to help Naruto. Kakashi would be calm as always and start to analyze the situation to figure out what caused the transformation.
Tsunade would probably be a bit surprised at first. She might be a bit protective of Shizune and would want to make sure Naruto is serious about her. Shikamaru might be the first to notice and just shrug it off as another strange relationship in the village. Sakura might be a bit jealous, not because she has feelings for Naruto in that way anymore, but because she's used to being one of the main girls in Naruto's life. And Kakashi? He'd probably just give Naruto some knowing looks and maybe some advice about relationships if Naruto came to him for help.
The Hyuga clan members would be very confused by 'Hanabi' (really Naruto). They would notice her (his) un - Hyuga - like behavior and attitude. For example, Naruto's loud and friendly nature would be a stark contrast to Hanabi's more reserved Hyuga self. As for Naruto's friends, they would be puzzled by 'Naruto' (actually Hanabi). They would wonder why he (she) seems a bit different in combat and decision - making.
The villagers in the Hidden Sound Village would likely be in awe at first. Some might be skeptical, but as Naruto starts to show his leadership and use his godlike powers for the good of the village, they would come to respect him. In Konoha, his old friends would be proud of him, but also a bit sad that he's leading another village. Villains in the Naruto universe would probably be more cautious, knowing that Naruto's power as Otokage could be a major threat to their plans.
Sasuke would likely be very suspicious. He has always had a complex relationship with Naruto, and this new, twisted Naruto would be a huge red flag for him. He might initially think it's a trick or some new form of power Naruto is trying to master, but as he realizes it's a real change, he would be on guard. Sakura would be worried and try to find a way to bring Naruto back to his old self. She has always cared about Naruto and would not be able to stand seeing him like this.
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.
Kakashi would be disappointed. He has trained Sakura and hoped she would grow into a great shinobi with good values. If she turns evil, he would feel like he has failed in some way. He would likely try to talk some sense into her, but if that doesn't work, he would have to take appropriate actions to protect the village from her actions.