Kawaki makes his appearance in Boruto manga at a specific point, but I can't recall exactly. You might want to check the official manga sources for the precise chapter.
Many of Naruto's friends and allies would be filled with rage. Characters like Sasuke would probably seek immediate revenge on Kawaki. The other villages might also see this as a sign of instability in the Hidden Leaf and could either try to take advantage or offer help depending on their relationships with the Leaf. And the younger generation, like Boruto, would be deeply affected. He would have to deal with the loss of his father and might struggle with his own identity and purpose in a world without Naruto.
Boruto's reaction would be complex. He'd be heartbroken, for sure. He might start to question his own worth and purpose. But over time, he'd realize that he has to carry on Naruto's legacy. He'd become more serious and focused. He'd also become more empathetic towards others, understanding the weight of sacrifice. He might even start to study Naruto's techniques and leadership style more closely, trying to emulate the things that made Naruto such a great Hokage and hero.
It could also be related to a prophecy or a pre - determined fate in the fanfic's plot. There might be some kind of dark prophecy that says Kawaki has to kill Naruto to prevent a greater evil. Or perhaps Kawaki is being controlled by an external force that has a vendetta against Naruto and uses Kawaki as a tool to carry out the murder.
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.
Some fans might like it. They could see it as a way to show Naruto's strict parenting side and how he is trying to instill good values in Boruto. It would add a new dimension to their relationship.
He may try to understand Boruto's reasons. Naruto has always been one to look for the good in people. So, even when hurt, he might give Boruto the chance to explain himself. He could say something like 'Boruto, I know you didn't mean it. Let's talk about what's wrong.' He'll be patient and try to resolve the issue rather than getting angry right away.