One possible reason could be his strong bond with Naruto. Their relationship has been through so much, and Sasuke might realize that Naruto understands him on a deeper level than Sakura. Maybe he feels that his journey and growth are more intertwined with Naruto's, and he values that connection more in this fanfiction.
One possible reason could be his long - standing feelings for Sakura. Despite his journey and time with Karin, his original connection with Sakura might have resurfaced. Sasuke has known Sakura since they were young, and those early memories and emotions could have influenced his decision.
Perhaps Sasuke starts to notice Ino's unique skills and how they complement his own. Ino has her mind - related jutsus which could be useful in certain missions or battles. This practical aspect, combined with a growing personal bond, might lead him to leave Sakura for Ino.
One possible reason could be Sasuke's pursuit of power. In many fanfictions, his thirst for greater strength might lead him to leave Sakura behind as he embarks on a solo journey to train in more dangerous and secluded places. He may feel that his goals are too dangerous for her to be involved with.
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.
Maybe she's just too heartbroken by Sasuke's actions and decides she needs a fresh start away from all the drama.
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.
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.
There are fanfics like that. Sasuke might leave Sakura for Karin because of Karin's loyalty. Karin has shown unwavering loyalty to Sasuke throughout the series. She was willing to risk her life for him on multiple occasions. In contrast, Sasuke might think that Sakura's love is more of a childhood crush that she hasn't fully grown out of, and he may be drawn to Karin's more mature and selfless loyalty.
One possible reason could be a difference in their goals. Sasuke has always been on a journey of revenge and self - discovery. If in the fanfic, Naruto's path starts to conflict with Sasuke's in a way that Sasuke can't tolerate, he might leave. For example, if Naruto decides to fully side with the village elders whom Sasuke distrusts, Sasuke could see this as a betrayal of their friendship and leave. Another reason could be an external threat that forces Sasuke to leave to protect Naruto. Maybe there's a powerful enemy that specifically targets Sasuke and he doesn't want Naruto to get caught in the crossfire, so he leaves without explanation to keep Naruto safe.
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.