Well, perhaps they leave to find answers about the Uchiha clan. Naruto, being Sasuke's friend, decides to accompany him. They could end up in some ancient ruins where secrets about the Uchiha are hidden. Along the way, they have to face challenges like lack of supplies and hostile ninjas who don't want them to uncover those secrets.
In this kind of fanfiction, one possibility is that they go on a journey to discover new jutsu together. They might leave the Hidden Leaf Village to find a place where they can train without the constraints of the village rules. Maybe they encounter new and powerful enemies that force them to rely on each other more than ever, strengthening their bond.
They might leave because they want to start a new life away from the chaos and politics of the village. Naruto and Sasuke could head to a remote island. There, they build a small settlement and start training the local kids in ninjutsu. They also use this time to reflect on their past and heal from all the traumas they've been through.
One possible scenario is that Naruto would be initially shocked. He has always seen Sakura as Sasuke's love interest. But he might accept her feelings gradually. Sakura, on the other hand, would have to deal with the guilt of leaving Sasuke. Naruto could help her through this and they might start a new life together, facing the challenges of the ninja world as a couple.
One possibility is that they go on a journey of self - discovery. Away from the constraints of Konoha, Naruto and female Sasuke might explore new jutsu and powers. They could encounter new enemies and allies, and perhaps form a new ninja group that operates outside the traditional shinobi village system.
One possible reason in this fanfiction scenario could be that Sasuke feels a stronger connection to Karin on a spiritual or power - related level. Karin has unique abilities that might attract Sasuke more than Sakura's medical ninjutsu. Maybe he sees in Karin a kindred spirit in terms of their past traumas and the way they've had to fight to survive. Also, Karin has always been very devoted to Sasuke, and he might be drawn to that unwavering loyalty.
Naruto might initially be in denial. He's so used to having Sakura around and believing that they have a future together. So when she leaves for Sasuke, he might think it's just a temporary thing or that she's been influenced by something or someone. But as time passes and he realizes it's real, he would be deeply hurt. He might also start to question his own self - worth, thinking that he wasn't good enough for Sakura. And he might even try to win her back at first, but then slowly come to accept the situation and focus on his other responsibilities like being a ninja and protecting the village.
This type of fanfiction concept is really out of the ordinary. Naruto's character is built on his values of friendship, loyalty, and his dream of becoming Hokage. Killing Sasuke would mean betraying all of that. However, in a fanfiction, the author might be exploring the 'what - if' scenario. For example, what if Sasuke's actions against Konoha were so heinous that Naruto felt he had no choice? But still, it's a far - fetched and very different view from the original Naruto we know.
In this fanfiction, Naruto might be leaving with Tsunade for a top - secret mission. Maybe they are going to investigate a new threat that has emerged in a far - off land. Tsunade, being the experienced Hokage, could be guiding Naruto on this journey, sharing her wisdom and combat skills along the way.
Their relationship could deepen a great deal. Away from the village, they have only each other to rely on. This would make them more open and honest with one another. For example, Sasuke might finally share all his innermost thoughts and feelings about his family and his revenge plans with Naruto.
Perhaps they are forced to leave due to false accusations or being framed for something they didn't do. This could create a situation where they feel they have no choice but to leave Konoha in order to clear their names and also protect the village from the real threats that might be lurking in the shadows.
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.
One possible reason could be her long - standing and deep - rooted love for Sasuke. Since childhood, she has had strong feelings for him. Maybe in this fanfiction, she realizes that her feelings for Sasuke are unshakable and that she can't continue to be with Naruto while having such intense feelings for another.