Some of the more mature characters like Dumbledore (if they were to find out) might see it as a natural part of growing up. They could try to guide Harry and Hermione separately, understanding that this is a new and difficult area for them to navigate.
Ron would be furious. He's been friends with both Harry and Hermione for so long and has had his own unspoken feelings for Hermione. His reaction could range from shouting at Harry to giving them both the cold shoulder for a while.
Dumbledore's reaction could be complex. He might feel guilty for not realizing it sooner. In some fanfictions, he would try to make amends by providing more support and protection to Harry. Other teachers at Hogwarts, like McGonagall, would be sympathetic and might offer their own forms of help, like extra tutoring or a place for Harry to relax.
Well, in some fanfics, it can create an immediate awkwardness. Their friendship might be put on hold as they both struggle to deal with this new and rather uncomfortable topic. Hermione, being the more reserved one, might be shocked and pull away from Harry at first.
As for the teachers, Dumbledore would be calm and try to understand the situation. He might see it as an opportunity for Harry to learn something new about himself and magic. Snape, on the other hand, might be sarcastic and critical, blaming Harry for getting into such a situation, but secretly he might also be intrigued by the magic used.
Harry would likely be very protective of Hermione. He's her best friend, after all. He might confront Draco immediately and try to get Hermione to see that she doesn't deserve this. Ron would probably be angry too, and might even be more impulsive in his reaction, perhaps getting into a fight with Draco.
Some might be shocked. Hermione, for example, would probably be very concerned about the use of a Muggle weapon in the wizarding world and its implications. She might worry about how it could change the balance between the Muggle and wizarding communities.
Some characters might be shocked. For example, Sasuke could be surprised as he has his own complex relationship with both Sakura and Naruto. Kakashi, being their sensei, might be disappointed but also try to be understanding and help them through the situation.
One common plot is the 'slow burn' where Harry gradually realizes his feelings for Hermione over time. It might start with him getting jealous when Hermione spends time with other guys. Another plot could be a 'what - if' scenario, like what if Harry had realized his feelings earlier in the series and how that would have changed the events of the books.
One common theme is the exploration of friendship boundaries. When Harry is hurt by Hermione, it often shows how far a friend can go before crossing a line. For example, in many fanfics, Hermione's over - intellectualizing or her strong - willed nature causes her to accidentally harm Harry's feelings or even physically hurt him in some cases.
Friendship is a very common theme. Their strong bond as friends in the original series often gets expanded upon in fanfics. Writers might show them having deep conversations and relying on each other even more.