At first, Naruto is probably shocked and confused. He might not understand why the village would take such a harsh step just for hurting Sasuke. He may feel betrayed, especially if he thought he had friends and allies in the village.
Well, Naruto might be furious. He's always been protective of Sakura. He'd probably drop everything he's doing and go after Sasuke to rescue Sakura. Naruto has a strong sense of justice and loyalty, especially towards his friends. And Sakura is one of his closest friends, so he won't stand by and let her be in danger.
She could be heartbroken. Sakura has always loved Sasuke deeply, so his leaving for Naruto would be a huge blow to her. She might initially be in denial, not believing that Sasuke would choose Naruto over her.
As a fan of online literature, I don't have the experience or knowledge to answer this question. However, according to the online novel resources that I know, I can search and check the plot of Naruto: My Wife Is Sasuke to find a novel that is similar to the plot. However, please note that due to the wide variety of online literature works, it may not be easy to find completely similar or identical plots.
Honestly, 'y f n' in fanfic could be a random combination of letters without a widely recognized meaning. Maybe it's a made-up term by the author for a special plot element or character trait.
Some in the ninja world would likely be shocked at first. The idea of Naruto and Sasuke having a son together goes against the traditional views of many. But those who are close to them, like their friends from Team 7, would probably be supportive. Kakashi, for example, might see it as a new step in the evolution of the ninja world's relationships. However, there would also be those who oppose it, especially from more conservative clans who might fear the implications of such an unorthodox union on their power structures.
I'm not entirely sure specifically what that particular 'bts y n is a hybrid hurt fanfiction' is about without more context. It could be a fan - created story that involves the BTS members, some kind of 'y n' (which might be a made - up or specific character in the fanfic world), and it's a 'hybrid' concept which could mean a mix of different elements like human and something else, perhaps supernatural, and 'hurt' might imply there are elements of pain or emotional distress in the story.