Sasuke could end up in a very dark place. He might get involved with some really bad characters or groups that could lead him further astray from his original path. He could lose his sense of self and become consumed by revenge or whatever negative emotions are driving him to leave in the first place.
One possible reason could be that he finally realizes Sakura's unwavering love for him. Throughout their time apart, he might have come to understand how much she truly cared, and now he regrets not being there for her. Also, he could have seen how she grew stronger on her own and feels he missed out on being part of that growth.
It could start with Naruto getting a mysterious message or a vision that tells him he and Sasuke need to leave together for the greater good. He then goes to find Sasuke and convinces him to come along.
Naruto could also use his new jutsu or skills he has acquired. He might show Sasuke that he has become stronger and that they could face whatever Sasuke is running from together. He could block Sasuke's path physically and then start talking some sense into him, like how leaving won't solve his problems but will only create more.
Their relationship would go through several stages. Initially, there would be a sense of unease as they are leaving their home. However, as they journey on, they will encounter various difficulties. For example, when they are short on food and supplies, they have to work together to find resources. This kind of shared experience would make them more empathetic towards each other. Sasuke, who has always been reserved, might open up more about his family and his quest for revenge in a more sincere way to Naruto. Naruto, in turn, would share his insecurities about being the Jinchuriki. Over time, their relationship would evolve from comrades to true friends who are willing to sacrifice for each other.
In the fanfic, they could leave the village in search of a long - lost ninja art. They believe this art could be the key to bringing peace to the ninja world. During their travels, they encounter various enemies who also seek the art. Sasuke and Sakura must use their skills and teamwork to overcome these foes and continue their quest.
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.
Sakura could be a bit angry at first. She has grown and become more independent during his absence. When Sasuke shows regret, she may lash out, expressing all the pain and frustration she felt during his long absence, but deep down she still has feelings for him.
One possible motive could be that Sasuke is so consumed by his thirst for power and revenge that he sees Sakura as a liability or a distraction. He might think that she would try to stop him from leaving the Leaf Village to pursue his own dark path, and in his warped state of mind, decides to eliminate her.
One possible plot twist could be that they are being secretly manipulated by an unknown enemy who wants them out of Konoha for some dark purpose. Maybe this enemy has spread false rumors about them in the village, making them feel like they have no choice but to leave. Another plot twist might be that they discover a long - hidden truth about their families that is connected to some ancient power outside of Konoha, which compels them to leave in search of answers.