Sasuke would be completely shattered. His world would be turned upside down. He had always seen Naruto as a rival, but also as someone important. Naruto sacrificing himself for him would make Sasuke reevaluate his entire life. He would feel an overwhelming sense of guilt and would likely isolate himself from others. However, over time, he would start to use Naruto's sacrifice as a motivation to become a better person and to protect the things Naruto held dear. He would start to follow in Naruto's footsteps in terms of values like friendship and loyalty, and would try to make amends for his past mistakes.
Sasuke could also have a complex mix of emotions. On one hand, he has a long - standing relationship with 'Naruto' as a male friend. Now that he knows Naruto is a girl, he might start to feel a different kind of connection. He may become more protective, but also a bit confused about his own feelings towards this new - found knowledge. He might even feel a bit betrayed that Naruto has hidden this fact for so long.
Sasuke might be initially shocked. He has always seen Naruto as a rival and suddenly finding out Naruto is a girl could completely change his perception. He may start to view Naruto in a more protective way, as his traditional views of gender roles might make him feel the need to safeguard her now that he knows she's female.
One possible plot development could be that Sasuke is initially in a situation where he is facing an enemy he can't defeat alone. Naruto steps in and gives his life to save Sasuke. This would lead to Sasuke being filled with guilt and a new sense of purpose. He might vow to carry on Naruto's will, perhaps trying to bring peace to the ninja world in Naruto's name. Sasuke could also start to question his own actions that led to Naruto having to sacrifice himself, and he may become more empathetic towards others as a result.
Sasuke might be in shock at first. He can't believe that Naruto is dying in his arms. He may feel a great sense of guilt, thinking that he could have done more to prevent it.
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.
On the other hand, Naruto could also have some hidden feelings that he wasn't aware of before. So, instead of being angry or shocked, he might start to have a warm feeling inside and start to question his own feelings towards Sasuke.
Naruto might initially be shocked. Given his friendly nature towards Sasuke in the original story, he wouldn't expect such an attack from her. So, his first reaction could be pure disbelief.
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.
His friends like Shikamaru would be deeply affected. Shikamaru, who had always respected Naruto's tenacity, would be at a loss. He might think about all the times Naruto pushed forward despite the odds and feel guilty for not being able to prevent his death. Hinata would be inconsolable. She had deep feelings for Naruto, and his sacrifice would shatter her world. The other ninja from different villages that Naruto had befriended during his journey, like Gaara, would also be in mourning. They would see Naruto's sacrifice as a noble act that inspired them to be better protectors of their own villages and to work towards a more unified ninja world.
She would be devastated. Hinata has always loved Naruto deeply. His sacrifice would shatter her world. She might initially go into a state of shock and denial. But eventually, she would become stronger, using her love for Naruto as a driving force to do good in the shinobi world.