On the other hand, Sasuke could be worried. He may think that Naruto is in some kind of trouble or danger. Given their history and the care they have for each other in the SasuNaru dynamic, Sasuke's concern could lead him to be more protective. He might start investigating the situation on his own to figure out why Naruto is hiding his face and ensure his safety.
He could feel a sense of guilt. Sasuke might think that his actions or their relationship issues pushed Naruto to leave. He may then set out to find Naruto, not only to bring him back but also to resolve their long - standing issues. For example, if there were unspoken words or unresolved fights between them, Sasuke would see this as an opportunity to set things right.
One possible reason could be that Naruto is hiding his face to conceal his emotions. In SasuNaru fanfiction, their relationship is often complex and full of unspoken feelings. Naruto might be afraid that Sasuke will read his true feelings if he shows his face. For example, if Naruto has developed deeper romantic feelings for Sasuke, he may not be ready to expose them, so he hides his face as a form of self - protection.
Naruto would probably be really angry at first. He's a free - spirited person who doesn't like being forced into things. So he'd likely try to fight back right away, yelling at Sasuke about what he's doing.
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.
One possible reason could be that he is on a secret mission and doesn't want to be recognized. He might be infiltrating an enemy organization or spying on someone. Another reason could be that he has some new power or mark on his face that he wants to keep hidden until he fully understands or masters it.
Sasuke could be one of the people who help him. Despite their past differences, they have a deep bond. Sasuke has his own skills and knowledge that could be useful in Naruto's situation, like his Sharingan abilities which could help in detecting enemies while Naruto is hiding his face.
Well, Sasuke could show his jealousy in a more subtle way too. He might start training harder or trying to outdo Naruto in certain skills when he feels threatened by someone else's relationship with Naruto. Sometimes, he might give Naruto the cold shoulder but then secretly keep an eye on him to see who he's with. It's all about that complex dynamic between them in the fanfiction world.
Naruto might initially be in shock. He's a very loyal person, so he wouldn't expect such a betrayal. He could try to talk to her to understand why she did it. For example, he might say something like 'Why? I thought we were in this together.'
Sasuke might also be angry. Angry at the situation, angry at whoever or whatever caused Naruto's amnesia. His anger could fuel his determination to find a cure. He would push himself and Naruto harder in training, hoping that it would jog Naruto's memory, all while trying to hide his true feelings of worry and fear for Naruto's well - being.
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.