With Naruto, it would be a huge shift. Naruto has always seen Sakura as a friend from Konoha. If she joins Akatsuki, Naruto would be confused and probably try to convince her to come back. Their relationship would become strained as they would be on opposite sides, at least initially. Naruto might see her as a lost friend that he needs to save.
Naruto and Sasuke's relationship might become more complex. On one hand, they are in a new and dangerous environment together, which could strengthen their bond as they rely on each other. But on the other hand, the ideology of Akatsuki might put some strain on their relationship if they have different views on how to handle the situation within the organization. For example, Sasuke might be more inclined to use force while Naruto tries to find a more diplomatic solution.
Sakura's character would experience a huge transformation. Her joining the Akatsuki means she has to interact with a group of outcasts and villains. This would make her more street - smart and less naive. She would also have to hide her true feelings, which could make her more introverted in a sense. Her medical skills would still be an asset, but she might have to use them in ways she's not used to, like healing enemies of the Leaf Village, which would be a big moral struggle for her.
Her character could develop a darker side. Being around the Akatsuki, who are often associated with more morally ambiguous actions, might make her question her previous beliefs. She could become more ruthless in combat and decision - making.
She would become more adaptable. The Mist's different environment and fighting styles would force her to change. Her physical skills might improve as she trains with Mist ninja who have different combat techniques. For instance, she could learn to be more stealthy like the Mist assassins.
Naruto would be devastated. He's always been one to value his friends deeply. He might initially go into denial and then be filled with rage, vowing to find out who or what was responsible for her death and seek justice. He would also likely carry a great deal of guilt, thinking that he should have been able to prevent it.
In a fanfiction where Sakura Haruno joins the Akatsuki, it could start with her being captured by them. Instead of killing her, they see her potential. She then has to adapt to their way of life. She might learn new jutsu from them. But she would also be constantly torn between her new comrades and her old friends. She could try to find a middle ground, where she can use the Akatsuki's resources to protect both the Akatsuki members who have some good in them and her friends from the Leaf Village.
The dynamic would be turned upside down. Sasuke would likely become more of an outcast or a loner, feeling rejected. Naruto would be in a difficult position, having to balance his friendship with Sasuke and his new relationship with Sakura. Sakura would be the catalyst for this change, and she would have to face the consequences of her actions, like dealing with the villagers' opinions and the potential backlash from Sasuke's supporters.
If evil Naruto were to join Akatsuki in fanfiction, the story's moral compass would shift. Akatsuki is already seen as a villainous group, but with Naruto on board, it becomes even more of a gray area. Naruto's relationships with characters like Kakashi and Jiraiya would be completely different. They would probably try to save him from his evil ways, but it would be much more difficult. The power struggles within Akatsuki would intensify as members vie for Naruto's loyalty or try to keep him in check. And the overall plot would likely focus more on Naruto's actions and how they impact the ninja world in this new, dark role.
Naruto's relationship with his sensei, Kakashi, would be severely strained. Kakashi has always been a guiding figure for Naruto, and Naruto joining the Akatsuki would seem like a betrayal. However, Kakashi might also suspect that Naruto has an ulterior motive. As for his relationships with the other Konoha ninjas, they would be filled with suspicion and mistrust. But Naruto could also form new relationships within the Akatsuki. He might befriend some of the members who have a bit of good in them, like Konan perhaps, and together they could work towards a new future for the Akatsuki.
The relationship between Naruto and Sakura would become much more strained yet also more intense. Sakura would be constantly worried about Naruto's safety in Akatsuki. Naruto, on the other hand, would be in a difficult position as he's in an enemy organization but still cares about Sakura and Konoha. His relationships with the Akatsuki members would also be complex. Some might see him as an opportunity, while others might be hostile. Sakura's relationship with the rest of Konoha would also be affected as she tries to support Naruto from afar.