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.
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.'
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.
Naruto might have a mixed reaction. He could laugh at the funny parts of the fanfiction. However, if the fanfiction misrepresents his friends or his village in a negative way, he might get angry. He's very protective of those he cares about. He may also be intrigued by the different versions of himself that are presented in the fanfiction, and might even start to think about how he can grow in those new directions.
Sasuke would be furious. He already has a strong sense of justice and loyalty to Naruto. He'd likely immediately start looking for Naruto, using his Sharingan to track any possible leads. He might even go against the village rules if he thought the village was involved in Naruto's kidnapping.
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.