His friends could have mixed reactions. Hermione would likely be curious and want to discuss the themes and stories within the phoenix fanfiction. Ron might think it's a bit odd but would go along with it. Ginny, being more in tune with Harry's adventurous side, might actually want to read some of the fanfiction with him.
They might be a bit surprised at first. But then they would probably be understanding. Hermione, for instance, might be interested in the literary aspects of the fanfiction he likes. Ron, on the other hand, might tease him a bit but still support his interest.
If his friends discovered this, it would be an interesting situation. Hermione would probably analyze it from an intellectual perspective, looking at how the phoenix is portrayed and what it means in the context of the fanfiction. Ron might make some jokes about it, but deep down he would respect Harry's interest. And Ginny, she might see it as another aspect of Harry's complex personality and be more accepting, perhaps even sharing some of her own thoughts on phoenix - related stories she's heard.
Sasuke would probably be dismissive at first. He'd think it was a waste of time and Naruto should focus more on their ninja goals. But secretly, he might be a bit curious himself. Sakura would likely be surprised and might tease Naruto a bit about it, saying he should be more interested in medical ninjutsu or something more relevant to their village. Shikamaru, on the other hand, would just sigh and say it's too troublesome for him to care, but deep down he'd understand Naruto's need for something different.
His friends might be really shocked at first. They know Naruto as a ninja, not someone who sings fanfiction. Some might find it hilarious and start teasing him in a friendly way. For example, Shikamaru might say something like 'Only you, Naruto, would come up with something so strange.'
Hermione would probably be very shocked at first. She has always seen Draco as the enemy, so it would take her a while to come to terms with it. Ron might be more vocal in his opposition, thinking it's a really bad idea. But if they saw how happy Harry was, they might gradually warm up to the idea.
Their friends' reactions could vary widely. For instance, Choji might be really excited and start planning big celebratory feasts for them. He's always been a friendly and positive guy. Kiba might be a bit more nonchalant about it, but still offer his congratulations. However, some of the more perceptive friends like Hinata might have already suspected something was going on. She would be very understanding and supportive, and might even give Sakura some advice on how to handle a relationship with someone as complex as Sasuke. The older generation, like Kakashi, would probably be a bit more reserved in their reactions. He might give Sasuke some stern advice about treating Sakura right, while also being happy for the two of them.
Harry would likely be quite curious. He'd want to know what these fanfictions were about. Maybe he'd be a bit cautious at the same time, worried that some of the fanfictions might distort Sirius's true character. But overall, I think he'd be intrigued and might even try to find a way to read some of them, just to see what the fuss was all about.
Sasuke would likely act like he doesn't care much. But secretly, he might be a bit intrigued as to why Naruto is into such things. He might think it's a waste of time or he could see it as another way Naruto is different from him.
Sakura might tease Naruto about it a little. She'd probably think it's a bit strange that he's interested in something so different from their own world. But she'd also be curious to know what it's all about.
If their friends found out, Kiba might tease Naruto a little bit, but in a friendly way. He respects Hinata and Naruto, so he'd be okay with it. Ino would be all excited and would start asking Hinata for details. She's always interested in romantic stuff. Lee would be super positive and give Naruto a big thumbs - up, saying something like 'Youthful love is wonderful!'. And Neji, if he were still alive, would be very protective of Hinata at first, but then see how happy Naruto makes her and be supportive.
Harry would probably be shocked at first. He respects Remus a great deal, but Hermione is like a sister to him. He'd need some time to come to terms with it. Ron, on the other hand, might be more openly opposed. He has always had a bit of a protective streak when it comes to Hermione, and he might think Remus is too old for her. Ginny would likely be more understanding and might try to mediate between the others.
Harry and Ron would probably be shocked at first. Ron might be a bit scared, but Harry would quickly see the potential in Hermione's new ability. They would likely be proud of her for achieving such a difficult transformation and would support her in using it for good.