Kakashi might be initially surprised. But then, he would probably use it as a teaching moment for Naruto. He could say something like 'Naruto, stealing is not the way of a ninja.' And then give him a punishment like extra training.
Sasuke might be initially shocked. He's always been in a sort of competitive relationship with Naruto. But then he might see it as a sign of Naruto's growth and need for family. Sakura would probably be really happy for Naruto. She knows how much Naruto has yearned for a family, and she would see Kakashi as a great father figure for Naruto. As for the older generation like Tsunade, she might be a bit hesitant at first, but then she would support it, seeing that it gives Naruto more stability.
Well, Shikamaru would be one of the characters who would take Naruto's sacrifice very hard. He had always respected Naruto's determination. His reaction might be to become more serious about his duties in the village, feeling that he needs to step up in Naruto's absence. Hinata would be heartbroken too. She had deep feelings for Naruto. She might struggle to come to terms with his loss but also find strength in his selfless act. And all of the Konoha 11 would be united in their grief, vowing to protect the village and each other more fiercely in Naruto's memory.
Naruto would be extremely devastated. He sees Kakashi as a mentor and father figure. He might go into a period of deep depression at first, but then turn his grief into motivation to become stronger. Sakura would also be very sad and might focus more on her medical skills, vowing to save more lives in Kakashi's memory. Sasuke might have a more internal reaction, feeling guilty if Kakashi died protecting him, and it could further fuel his own goals, whatever they may be at that time.
The other villages might react with a mix of shock and suspicion. They knew Naruto was a powerful force for good in the ninja world. His death could be seen as a sign that something was amiss in Konoha. Some villages might even fear that Konoha was becoming unstable and could pose a threat. Characters like Gaara, who had a special bond with Naruto, would be deeply saddened and might try to find out the real reason behind Naruto's death.
Kakashi's reaction would be complex. He is a man who has lost many people in his life. But Naruto was special. He would hold Naruto tightly, his hands trembling slightly. He might try to use some of his own chakra to keep Naruto alive a little longer, but deep down he knows it's futile. His face would show a mixture of pain, regret, and love. He would remember all the times he trained Naruto, all the lessons he taught him, and how Naruto had surpassed all expectations.
Kakashi would likely be very concerned. He would immediately assess Naruto's injuries. If they were serious, he would use his medical skills to start treating him right away. His first reaction would be to make sure Naruto was stable and out of immediate danger.
Kakashi might immediately offer a comforting presence. He could put his hand on Naruto's shoulder and just be there silently, letting Naruto know he's not alone.
Kakashi may also get angry. Angry at the people or things that caused Naruto to get those scars. This anger could fuel his determination to make Naruto stronger, so that he can better defend himself in the future. He might then intensify Naruto's training, all while having a new - found sense of protectiveness towards Naruto.
Sakura is strong - willed and determined. Kakashi, on the other hand, is more laid - back yet highly skilled. Sakura's determination can inspire Kakashi to be more involved at times. For example, when she is really passionate about a mission, it can make Kakashi step up his game too.