Sasuke might initially be shocked. He has always seen Sakura as someone connected to Konoha, so her leaving would be unexpected. He could be concerned about her safety, especially if she leaves without proper preparation or protection.
He might also feel a sense of guilt. If he believes that his actions or his past relationship with Sakura in some way contributed to her decision to leave, he would be wracked with guilt. For instance, if he had previously rejected her too harshly, and she now feels she needs to leave to get over him. He could then set out to find her to make amends.
Sakura's reaction would depend on how the author writes her character development. If she's become more confident in herself, she might approach Sasuke with a more assertive attitude. She could tell him that she's not the same girl he left behind. However, she'd still have that underlying love for him. She might also be worried about how the village will accept Sasuke's return and how it will affect her standing in Konoha. So her reaction would be a complex blend of personal feelings and concerns for the village.
At the beginning, their relationship might be a bit rocky. Sasuke is used to being alone, and Sakura has to adjust to his way of doing things. However, as they face challenges together, like fighting off enemy ninjas or surviving in harsh environments, they start to bond. Sakura's constant support and her growth as a ninja start to make Sasuke respect her more. Eventually, this respect could lead to a more intimate relationship where they truly open up to each other.
Naruto would be devastated. He has always considered Sakura as a dear friend and teammate. He would probably try to convince her to come back at first. If that fails, he might see it as his mission to bring her back by force if necessary, believing that she has been led astray. Sasuke, on the other hand, might have a more complex reaction. He has his own issues with Konoha, so he might understand Sakura's desire to leave on some level, but he would also be suspicious of her motives for joining Akatsuki.
One possible plotline could be that Sakura leaves Konoha due to a personal quest for self - discovery. She might feel that she has outgrown the village or that there are things she can't achieve while staying there. For example, she could be in search of a new medical ninjutsu technique that can only be found in a far - off land. Along the way, Sasuke might cross her path, and they could either have a moment of reconciliation or further conflict depending on their respective states of mind.
On the other hand, their relationships could grow stronger. Away from the rules and expectations of Konoha, they rely more on each other. Naruto and Sasuke could finally understand each other better. Sakura, with her medical skills, becomes even more important to them. They start to trust each other more deeply, and their bond as a team becomes unbreakable. They might have heart - to - heart conversations that they never had in Konoha.
For Naruto, it would be a big shock. He's always seen Sakura as an important part of the team. He would probably feel guilty, thinking he might have done something wrong. Sasuke might be more reserved in his reaction, but deep down, he would also feel the loss. Kakashi would be worried about her safety. The other ninja in Konoha might start to question the unity of the village if someone like Sakura, who was so well - known, left. And the young ninja who looked up to Sakura would be disappointed and might even lose some motivation in their training.
Another reaction could be that Sakura tries to follow Sasuke. She believes that she can change his mind or that she can be of help to him. She might leave her own responsibilities behind for a while to chase after him, thinking that their bond is strong enough to overcome whatever is making Sasuke leave.
One possible fanfiction could be that Sasuke returns to Konoha after a long mission. Sakura, who has been longing for his return, discovers she is pregnant. This news brings a mix of joy and worry. The village of Konoha is also excited as it means a new generation is coming. Sasuke might initially be shocked but then becomes determined to protect his family and the village.
One possible plotline could be that they leave to seek a new form of power. Maybe they've discovered a threat that the Hidden Leaf isn't aware of, and they believe they can find a solution outside. Another could be that they're on a journey of self - discovery. Sakura has always been in Sasuke's shadow to some extent, and this could be her chance to truly find herself while being with him. Also, perhaps they leave due to some political unrest in Konoha that they don't want to be a part of.
One possible plot could be that they leave Konoha due to a new threat that the village is unable or unwilling to face. They might go on a journey to find a way to defeat this threat on their own. Along the way, they could face many challenges that test their friendship and skills.