At first, his friends would be in a deep state of mourning. Ginny might be inconsolable, having lost the love of her life. Neville would feel a great sense of loss as Harry was a symbol of hope for him. However, as time passes, some of them might start to suspect that Harry isn't really dead. They might notice strange magical occurrences that seem to be related to Harry, like objects he once owned behaving oddly. This would lead them on a journey to discover the truth about Harry's supposed death.
His friends would likely be devastated at first. Hermione, for instance, might throw herself into research to find out what really happened, believing there has to be a way to bring him back. Ron would be in a state of shock and anger, feeling like he failed to protect Harry. They would probably also start to question their own actions and whether they could have done something differently to prevent Harry's 'death'.
His friends would react in a very emotional way. Hagrid would be heartbroken and would probably retreat to his hut, feeling like he lost a part of his family. Luna might have a more spiritual take on it, believing that Harry's essence still exists in some form and that he will return. The Weasley family as a whole would be mourning, but also would be determined to find out if there was foul play involved in Harry's disappearance that led to the belief of his death. They would start to investigate, using their various connections in the wizarding world.
Hermione would probably be devastated at first. She might throw herself into researching ways to bring Harry back or to find out if he's truly dead. Ron would be angry and feel guilty, thinking they should have protected Harry better. Ginny, on the other hand, would be heartbroken but also determined to carry on Harry's legacy.
He might be very sad at first. Harry has always valued his friends, so being forgotten by them would be a huge blow.
Hermione would be heartbroken as well. She would likely try to find a way to bring Lupin back, delving deep into the library's restricted section for any possible spells or solutions. She would also be the one to comfort Harry and Ron, using her logic to try to make sense of the senseless loss.
Hermione would immediately start researching ways to heal him. She'd pour over ancient books and consult with the most knowledgeable wizards to find a cure or at least a way to ease his pain.
At first, his friends would be shocked. Hermione might think it's some kind of dark magic at first glance. But as Harry shows them what he can do, she would start to analyze it scientifically. Ron would be more awed. He'd be like a kid seeing a new cool trick. They would both support Harry in exploring this new ability, but also be a bit cautious as they don't fully understand where it comes from or what the implications are in their wizarding world.
His friends would be very surprised. Hermione would probably be a bit skeptical at first. She'd want to research all about Witchers before she fully supported Harry's new interest. Ron, on the other hand, might be more excited. He'd see it as another adventure and would be eager to hear all about the Witcher world from Harry.
Ron would probably be both shocked and a bit awestruck at first. He might make some typical Ron - like jokes to ease the tension, like 'Blimey, Harry, you're a dragon! At least you'll be good for scaring off Snape now!'. But deep down, he'd be worried and determined to help Harry get back to normal.
His friends would be quite shocked. Neville might be a bit scared at first, thinking it's some new dark magic. But then they'd all come together. Ginny would probably be the one to try and comfort 'cat - Harry' by giving him some fish or milk, thinking that's what cats like. And they'd all be determined to get him back to normal as soon as possible.
Luna would likely have a very unique reaction. She might say that the fanfiction is just another form of magic in the world of imagination. She could tell Harry that he should embrace it in a way, as it shows how much people are interested in his story, even if it is a bit mortifying at first. But she would also respect if he was really bothered by it.
Hermione would probably be both curious and concerned. She'd want to research immediately to find out how and why this happened. Ron, on the other hand, might be a bit more in awe at first. He'd likely make some jokes about Harry looking like a strange bird, but still be supportive.