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.
His other friends like Shikamaru would probably just shrug it off and say it's typical Naruto behavior. They know he's always interested in new and different things. However, Choji might be interested to see if there's any fanfiction about food in the anime world, and they could end up having a long chat about it.
Sakura might be a bit surprised at first. She would probably tease Naruto a little about it, but then she'd also be curious to see what's in those fanfics. She might even start reading some herself to see how the fans portray her relationship with Naruto.
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.
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.'
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.
His friends would be shocked at first. Sasuke might feel a sense of responsibility to find Naruto and bring him back. Sakura would probably feel guilty, especially if she was somehow involved in the situation that led to Naruto being cheated on.
Sakura would be worried sick. She might immediately inform Kakashi sensei and the rest of the village. Then, she would probably want to be part of the rescue mission. Sakura has grown stronger over time and would use her medical ninjutsu and combat skills to help save Naruto. She would also be constantly worried about Naruto's well - being and would encourage the others to move faster.
Sasuke might be initially cautious. He would observe Cell carefully to assess his threat level. He could offer his Sharingan - enhanced perception to help Naruto in the fight. Sakura, she would be worried about Naruto but also ready to jump in and heal any wounds. Shikamaru might be thinking of strategies in the background, trying to come up with a way to outwit Cell using his intelligence.
His friends' reactions would be diverse. Naruto's more hot - headed friends like Kiba might be excited about the new firepower the modern army brings. They might want to jump right into using the guns and other weapons. But Naruto's calmer friends like Neji (if he were still alive in the fanfiction) would be more cautious. They would worry about the long - term effects on the ninja world, such as the potential for mass destruction and how it would change the balance of power. And Ino might be interested in how the modern army's communication systems could be used to improve their own ninja intelligence networks.
His friends would likely be shocked and deeply concerned. Sasuke might put aside their differences and be by Naruto's side, offering his support.
Sakura might be a bit surprised at first. But she would probably be happy for Naruto as long as he is happy. She might also be curious about the elf and want to learn more about her. Sasuke would likely be more reserved in his reaction. He might not show much emotion on the surface but deep down he would be glad that Naruto has found someone. Kakashi would probably give Naruto some sage advice about making a relationship work, especially since it's with someone from a different species.