The story would progress with a lot of tension. Naruto and Sakura joining Akatsuki would mean they are now on the opposite side of their former comrades in Konoha. There would be battles and skirmishes where they have to fight against their old friends. At the same time, within Akatsuki, they would be trying to influence the group towards a more positive path. Their character development would be interesting as they adapt to the new environment and face new enemies and allies within Akatsuki.
In fanfiction, if Sasuke and Sakura joined Akatsuki, it could lead to a complete shift in the power dynamics. Sasuke already has a complex relationship with the Akatsuki members. With Sakura by his side, she might act as a moral compass for him. Maybe they would try to reform the Akatsuki from within, or they could be forced to carry out some dark missions that would test their relationship.
If Sakura joins the Akatsuki in fanfiction, her character would likely become more self - reliant. In Konoha, she had friends and mentors to rely on. But in the Akatsuki, she would be among people who are not as trustworthy. This would force her to rely on her own skills and instincts more. Also, she might become more secretive. Since she's in a group that's not exactly friendly to Konoha, she'd have to keep a lot of things to herself.
If Naruto and Gaara became members of Akatsuki in fanfiction, the story would likely involve a lot of internal struggles within Akatsuki. The two of them would have to keep their true intentions hidden from some of the more hardcore and evil - minded members. At the same time, they could use their membership to gather information for their own villages. Their presence could also lead to new alliances within Akatsuki, as some members might be swayed by their ideals. And outside of Akatsuki, their villages would be in shock and confusion, not knowing what to make of their two heroes joining the enemy.
It could lead to a major shift in the power dynamics. Naruto's skills and ideals might conflict with the Akatsuki's goals, causing internal strife.
After being beaten, Naruto could start to explore different fighting styles or learn new jutsus that he hadn't considered before. Sakura, on the other hand, could gain more respect from the other characters. The story might then shift towards them teaming up in a different way, with Sakura taking on a more leadership role in their missions due to her victory over Naruto.
Sakura would likely become more ruthless. In her original setting, she is a healer, but in Akatsuki, she might have to be more combat - focused and less hesitant to use force. Ino would probably become more secretive. Her mind - transfer jutsu could be used for more devious purposes within Akatsuki, and she'd need to keep her true intentions hidden. Hinata might gain more confidence in a different way. Instead of being shy around her peers in Konoha, in Akatsuki she would have to assert herself among much more dangerous individuals. Tenten would change her view on weapons. Akatsuki's access to different types of dangerous weapons could make her more obsessed with obtaining and mastering them.
Naruto joining Akatsuki in fanfiction would turn his relationships upside down. His friends in the Leaf would initially feel betrayed. However, some might start to question if there's more to Naruto's decision. His relationship with Akatsuki members would be a mix. He'd be constantly in a tug - of - war with Itachi, who has his own plans regarding Naruto. And his interactions with Pain would be intense, as Pain represents a very different ideology from Naruto's. Naruto would have to struggle to find common ground or at least a way to coexist with these new 'comrades' while still holding onto his own values.
His relationship with Sasuke would become even more complex. Sasuke might be suspicious of Naruto's motives for joining Akatsuki, thinking he has truly turned to the 'dark side'. Or, they could end up on opposite sides of a conflict within Akatsuki itself if their goals within the organization differ.
Their relationship could become more of a mentor - mentee type. Itachi, being more experienced, could teach Naruto some of his ninja skills and strategies. Naruto, in turn, could help Itachi see the value in hope and friendship again. They might start to rely on each other more and more as they face the challenges within Akatsuki.
His personality might become more guarded. He'd be surrounded by people who are mostly out for themselves or have very different values from him. So, he'd need to be more cautious in showing his true self.