Naruto would be deeply hurt. He has grown up with so little love and acceptance in the village, and Hiruzen was one of the few people he thought cared for him. His reaction could involve a lot of self - reflection. He might question his own worth and what he has done wrong. But ultimately, his positive nature would take over. He would try to understand Hiruzen's reasons, even if he didn't agree with them. And he would strive to find a way to reconcile and make Hiruzen see that he is not a threat.
Sakura would be heartbroken. She'd likely spend hours upon hours by Naruto's side, trying to jog his memory with stories of their adventures together. She might even get a bit overbearing in her attempts. Sasuke, who has his own complex relationship with Naruto, would be conflicted. He'd see Naruto's forgetfulness as a sign of weakness at first but then realize the importance of their bond. Kakashi, being the experienced leader, would start by observing Naruto carefully to see exactly how much he has forgotten and then start a systematic process of helping him remember.
Sasuke would likely be devastated. Despite their past differences, Naruto was his rival and in a way, his closest friend. He might go into a deep state of regret and isolation. Sakura would be heart - broken. She loved Naruto, and his death would be a huge blow to her. She might become more withdrawn and focus all her energy on her medical ninjutsu. Kakashi would be filled with a sense of failure. He was Naruto's teacher, and he would feel responsible for not being able to protect him.
Sasuke might initially be indifferent on the surface, but deep down he would feel a sense of loss. He has always had a rivalry with Naruto, and Naruto's departure would mean an end to that dynamic. Sakura would be devastated. She has grown to care about Naruto as a friend and teammate, and his leaving would leave a big hole in the team.
Well, Sasuke might initially be a bit shocked but then he'd try to hide his concern. Sakura would be very empathetic and might immediately want to do something to help Naruto. Kakashi, being the experienced one, would take a more calm and strategic approach to deal with Naruto's situation and protect him from further abuse.
He might be really surprised. Naruto is used to his own world and the fanfiction could show things he never imagined. For example, if the fanfiction has his kids achieving great things in new ways, he'd be proud yet a bit shocked at how creative fans can be.
He might be shocked at how the village has developed. In some fanfictions, the village could have advanced technology. Naruto, being from a more traditional ninja world, would likely be both amazed and a bit confused at first.
He might be shocked at first. In fanfiction, the future could be full of unexpected changes. He could be excited to see how his friends and the village have developed. Maybe he'd be a bit sad if things didn't turn out as he hoped for his loved ones.
Well, they may react with a bit of nervousness too. The future in the fanfic could bring new challenges like changes in the music industry trends. For example, new technologies might require them to adapt their performance and promotion methods. They might worry about whether they can keep up with the fast - paced changes while still staying true to their art. But at the same time, they would also be determined to face these challenges head - on because they have always been a group that thrives on growth and evolution.