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.
His friends would most likely rally around him. Kiba might use his dog Akamaru to scout the area and make sure there are no other immediate threats. Hinata would be really worried and would try to use her Byakugan to see if there are any hidden enemies or if Naruto has any internal injuries. Choji would offer some of his food to Naruto to give him strength, as his clan's food can have special effects on a ninja's body.
One possible reason could be a misunderstanding. Maybe Naruto was misidentified as a threat in a tense situation. For example, if there was some sort of dark jutsu at play that clouded Kurenai's judgment and made Naruto seem like an enemy. Another reason might be that Kurenai was under some sort of mind - control. There are many villains in the Naruto universe who are capable of such things. If she was being controlled, she might unknowingly attack Naruto.
His relationship with Sasuke might be different. With Kurenai's influence, Naruto could be more understanding and patient, which might help him better deal with Sasuke's issues. His bond with Sakura could also change as he may approach her in a more mature way, having learned from Kurenai about relationships.
His friends would be extremely worried. They might immediately drop whatever they are doing to rush to his side. For instance, Thomas would be right there, trying to assess the situation and figure out how to help. He would be filled with a sense of urgency and determination to get Minho the care he needs.
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.