Shikamaru would be more laid - back in his approach. He would first assess the situation to see how badly Naruto was hurt. Then he would try to come up with a plan to resolve the issue, whether it's getting Kurenai to apologize or finding a way to prevent such a thing from happening again. He might also use his intelligence to try and understand what led to Naruto getting hurt in the first place.
Sakura would probably be very angry at Kurenai. She's protective of Naruto and would demand an explanation. She might even try to heal Naruto right away if it was a physical injury.
He might be shocked at first. Naruto is used to seeing Kurenai as an ally, so being hurt by her would be unexpected. He could immediately ask her why she did it. If it was a serious injury, he might struggle to stay conscious while trying to understand the situation.
Naruto would probably be really confused at first. He respects Kurenai, so he'd be hesitant to fight back right away. He might try to talk to her and ask what's wrong.
Sometimes, Naruto will try to understand his friends' motives. He's a very empathetic person deep down. So instead of just getting angry and staying that way, he'll try to figure out why his friends did what they did. He might even forgive them relatively quickly if he realizes they had good intentions, even if their actions still hurt him.
Naruto might be initially shocked and heartbroken. He is someone who values loyalty and friendship deeply, so being cheated on would be a huge blow to him.
Naruto would probably be initially cautious but also curious. He has a knack for seeing the good in people, so he might try to befriend the Akatsuki sister. Kurenai, on the other hand, would be more guarded. She is a more experienced ninja and would be wary of any Akatsuki member. But she also might see an opportunity to gain intel from the sister.
Sakura would be furious. She's always been protective of Naruto in the original Naruto series. In the RWBY fanfiction, she would probably start her own investigation to find out who was behind the betrayal. She might even challenge the RWBY characters if she thought they were involved. Kakashi, on the other hand, would be more calm and collected. He would try to analyze the situation rationally and figure out the best way to help Naruto.
Sakura might be initially surprised but would probably be supportive. She has always cared about Naruto's happiness, so as long as he is happy with the elf, she would be okay. Kakashi, on the other hand, would likely be intrigued. He's seen a lot in his life, but an elf - ninja union would be something new. He might offer some sage advice based on his own experiences with different cultures.
He would be heartbroken. Naruto values friendship above almost everything. At first, he might not believe it and try to reason with his friends.
His other friends like Shikamaru would think of the most practical solutions. He might calculate the risks of continuing the mission with a sick Naruto and come up with a plan. Maybe he'd suggest splitting the group, with some staying to take care of Naruto and others proceeding with the mission - related tasks that can't be postponed.
Naruto would be extremely hurt. He values his friends above almost everything, so their betrayal would be like a knife to the heart. At first, he'd probably be in disbelief and try to reason with them. When he realizes they won't listen, he might become angry and lash out. But deep down, he'd still hope to win them back.