Naruto could be in a state of shock at first. But then his determination would kick in. He'd recall all the times Sakura has been there for him and the team. Knowing that Sasuke has kidnapped her, he'd feel a sense of betrayal too, since Sasuke was once their teammate. He'd likely gather his friends and start planning a rescue mission right away.
Well, Naruto might be furious. He's always been protective of Sakura. He'd probably drop everything he's doing and go after Sasuke to rescue Sakura. Naruto has a strong sense of justice and loyalty, especially towards his friends. And Sakura is one of his closest friends, so he won't stand by and let her be in danger.
Sakura might initially be very angry. She has her own strength and pride, and being kidnapped by Sasuke, someone she once cared for deeply, would be a huge blow to her self - esteem. She could try to fight back immediately, using her medical ninjutsu skills and combat training to attempt an escape.
Sakura would probably be initially shocked and angry. She has always cared about Sasuke, and this betrayal would hit her hard. But she is also a strong - willed ninja. So, she would quickly gather her wits and start looking for ways to escape. She might try to use her knowledge of Sasuke's fighting style against him if she gets the chance.
She could be heartbroken. Sakura has always loved Sasuke deeply, so his leaving for Naruto would be a huge blow to her. She might initially be in denial, not believing that Sasuke would choose Naruto over her.
He may also choose to defend himself without really fighting back. Naruto values Sakura as a friend and teammate, so he would be reluctant to harm her. He might just try to dodge her attacks and keep talking to her, hoping to snap her out of it.
In some fanfictions, Sakura's reaction could be more complex. She might be hurt not just physically but also emotionally. This could lead her to question her relationship with Sasuke and might cause her to make some big decisions, like whether to continue trying to reach out to him or to cut him off completely.
Naruto might initially be in denial. He's so used to having Sakura around and believing that they have a future together. So when she leaves for Sasuke, he might think it's just a temporary thing or that she's been influenced by something or someone. But as time passes and he realizes it's real, he would be deeply hurt. He might also start to question his own self - worth, thinking that he wasn't good enough for Sakura. And he might even try to win her back at first, but then slowly come to accept the situation and focus on his other responsibilities like being a ninja and protecting the village.
Sasuke would likely be enraged. Naruto is his rival and also, in a way, his friend. He would immediately set out to find Naruto and confront Itachi. Sasuke has a strong sense of pride and would not let his brother get away with this.
In some fanfictions, Sakura may be determined to find Sasuke and bring him back. She could set out on her own journey, facing various challenges along the way, and growing both as a person and as a ninja in the process of trying to reunite with him.
Sakura might initially be a bit annoyed by Sasuke's possessiveness. She's a strong - willed woman, after all. But she also understands that it comes from his love for her and the baby. So, she may tolerate it to some extent.
Sasuke could also be confused. He has always had a mix of emotions towards Itachi, including love, hate, and envy. Being kidnapped by him would add another layer of confusion. He might wonder if Itachi has some new plan or if he's finally going to reveal some long - hidden truth. So, he might hold back on his full - fledged resistance and wait to see what Itachi has to say.