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.
At first, Naruto might be in shock. He has always trusted his friends, so the sudden betrayal would be a huge blow. He could be silent, unable to process what has just happened.
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.
There could also be friends who are so loyal to Naruto that they would consider following his request if they truly believe it's for the greater good. However, they would be deeply pained by it. Kakashi, for instance, might understand Naruto's selfless nature but would also struggle with the moral and emotional implications of taking his life.
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.
Kakashi would be the most perceptive. He'd see how Naruto singing 'Monster' is not just a random act but a way for Naruto to connect with his own fears and insecurities. His friends from the Hidden Leaf Village would overall be proud of Naruto for trying something new and for using the song to share a part of himself that they may not have fully understood before.
His friends would be shocked at first. Sasuke, for example, might see it as a sign of weakness on Naruto's part, that he let Minato do this to him. Sakura would be worried about Naruto's well - being and would try to find a way to reverse the process. Shikamaru would be thinking about the long - term consequences for the village and for Naruto's relationships. Overall, they would be very concerned and try to get Naruto back to his normal self.
Sakura might be shocked at first. She has always known Naruto as a regular ninja. But she could also be concerned and try to find a way to help him control his vampire side. Sasuke would probably be more cautious. He'd see Naruto as a potential threat, but also might be interested in how Naruto combines his ninja and vampire powers. Kakashi, on the other hand, would be calm and start observing Naruto to understand what has happened and how it affects the village.