There would also be some fans who might be a bit shocked. Naruto and Sasuke's relationship has always been complex and more of a deep friendship/brotherly bond in the original series. So a kiss might seem a bit out of character to them at first. But for those who love exploring different interpretations, they might come around to it and start to enjoy the new take on their relationship.
A lot of fans would probably start creating fan art based on this fanfiction. The kiss scene would inspire many different artistic interpretations, from cute and romantic to more angsty depending on how the fanfiction develops the story further. And of course, there would be intense discussions on fan forums about whether this is a good or bad development for the characters.
There would be other fans who might be intrigued. They like to explore different 'what - if' scenarios in fanfiction. They would see it as a creative way to explore the characters in a new light, even if it goes against the canon. However, they would also be aware that it's just a fictional alternative and not the real Naruto story.
On the other hand, Naruto could also have some hidden feelings that he wasn't aware of before. So, instead of being angry or shocked, he might start to have a warm feeling inside and start to question his own feelings towards Sasuke.
In this fanfiction, it might be that Sasuke got injured during the mission. Naruto, in a moment of relief after saving Sasuke's life, kissed him. This act could be the start of a new dynamic in their relationship, where they have to confront their feelings for each other while still completing the mission at hand.
Some fans are really into it. They enjoy seeing different takes on the Naruto and Sasuke relationship. It gives a whole new dimension to their dynamic. However, some fans might be a bit put off as it goes against the more traditional view of their relationship in the original anime and manga.
Sasuke would be furious. He's always been protective of Naruto in his own way. He would immediately start looking for her, using all his skills and resources. He might even go on a rampage if he thought Naruto was in serious danger.
A third group of fans might simply ignore it. They are so set on the original story and the positive portrayal of Sasuke and Sakura's relationship that they don't want to engage with any fanfic that goes against that. They might consider it a disrespect to the original creators' intentions for the characters.
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.
Some fans would be very disappointed. Naruto is a character that represents hope and friendship in the original series. So seeing him die alone in a fanfiction goes against the positive themes of the original. They might not like this dark take on the character.
There would be a lot of mixed reactions. Some hardcore fans who have dedicated a lot of time to writing Naruto fanfiction might feel betrayed. On the other hand, there are those who are more focused on the official Naruto products like the anime, manga, and games, and might not be as affected. However, overall, it would create a stir in the Naruto fan community and lead to a lot of discussions and debates.
Some fans would be extremely shocked and angry. Kushina is a beloved character, and Naruto slapping her goes against the loving relationship they should have as mother and son. They might feel that it's a disrespect to the original story's characters and themes.