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.
He could also become more vengeful. If Sakura's death was caused by an enemy, Sasuke would stop at nothing to avenge her. His focus would shift solely to seeking revenge, and his already formidable skills would be honed even further in his quest for retribution.
In many such fanfics, a common plot twist could be Sasuke choosing his revenge over Sakura. He might leave her without a second thought to pursue power or to face his enemies alone. This shatters Sakura's heart as she has deep feelings for him.
It could be out of jealousy. Sasuke might see Naruto as always hiding his true emotions and having this perfect image that others admire. By breaking the mask, he wants to expose Naruto's flaws and make himself feel superior. Or perhaps it's a way for Sasuke to assert his dominance over Naruto, to show that he can break through Naruto's defenses.
Well, in some versions of this fanfiction, it might be that Naruto uses a powerful and forbidden jutsu to defeat an overwhelming foe. This jutsu drains his life force, and Sasuke, who has just realized how much Naruto means to him, catches Naruto as he collapses. It could also be that Naruto is poisoned, and Sasuke tries his best to save him but fails in the end, and Naruto passes away in his arms.
One emotional moment could be Sasuke's realization of losing Sakura. His usually stoic facade might crumble as he holds her lifeless body, perhaps reminiscing about all their shared moments, from their early days as teammates to the more complex relationship they developed over time.
Anger could also be a part of her emotional response. After the initial heartbreak, she might be angry at Sasuke for not seeing her value, for not being able to return her love. And this anger could fuel her to either try to change his mind or to move on and become stronger without him.
One possible reason could be Sasuke's continued obsession with revenge. His single - minded pursuit of power and vengeance might make Sakura feel neglected and unloved in the relationship. For example, he often goes off on long and dangerous missions alone, leaving Sakura behind worried sick. Another reason could be a fundamental difference in their values. Sakura values life and healing, while Sasuke has been more focused on destruction in his quest for revenge.
One reason could be a fundamental difference in their goals. Maybe Naruto decides that Sasuke's pursuit of power in a certain way goes against his own beliefs of protecting the village and its people. For example, if Sasuke were to side with an enemy that Naruto sees as a threat to Konoha, Naruto might break the bond to protect his home.
Well, perhaps it's because of Sasuke's aloof nature. Naruto is a very open and friendly person, and constantly feeling shut out by Sasuke could lead to a break - up in the fanfiction. Also, Sasuke's thirst for power might be too much for Naruto to handle. Naruto believes in the power of friendship and hard work, but Sasuke seems to be constantly on a solo mission for more strength, which could create a rift between them.