The older characters such as Kakashi would be cautious. They would recognize Naruto but also be worried about the implications of someone from the future being in the present. They would want to know if his presence could change the future in a negative way. For example, they might fear that his actions could lead to the earlier awakening of a powerful enemy. As for the villains, they might see future Naruto as a threat and try to eliminate him as soon as possible. Orochimaru, for instance, would be very interested in Naruto's future powers and might try to capture him to study. And the new generation of ninja in the past would look up to future Naruto, seeing him as a symbol of what they could become.
Naruto would probably be really angry at first. He's a free - spirited person who doesn't like being forced into things. So he'd likely try to fight back right away, yelling at Sasuke about what he's doing.
Sasuke might also be angry. Angry at the situation, angry at whoever or whatever caused Naruto's amnesia. His anger could fuel his determination to find a cure. He would push himself and Naruto harder in training, hoping that it would jog Naruto's memory, all while trying to hide his true feelings of worry and fear for Naruto's well - being.
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.
Naruto might react with a sense of responsibility. If he saw a future where Konoha was in danger, he would feel it was his duty to do something about it. He could start by gathering information from the future vision, like the weaknesses of the enemy. Then, he would share this knowledge with his comrades and come up with a plan to protect the village.
At first, Naruto could be a bit skeptical. He might think it's some kind of trick or illusion. But once he realizes it's really his future self, he would be excited. He would want to know about his future family, if he has one. He'd also be interested in the state of the ninja world in the future. His reaction would be a mix of excitement, curiosity, and a determination to make sure his future turns out as good as his future self's seems to be.
Boruto might be in awe. He has always known his father as the Hokage, a powerful and respected figure. Seeing Naruto's past full of struggles, loneliness, and determination would make him realize how far his father has come. It could also make Boruto more empathetic towards Naruto and perhaps inspire him to be more like his father in some ways.
Sasuke, on the other hand, might be more conflicted. He has his own goals and ideals. If he saw a future that didn't align with what he wanted, he might first question the vision. But ultimately, he could also take steps to change it, especially if it involved the safety of his village or his loved ones like Naruto or Sakura. He has a complex personality, so his reaction would not be straightforward.