Their relationship could start as comrades on a mission. As they leave Konoha together, they'll have to rely on each other. Naruto's sunny personality might gradually break through Samui's more reserved nature. They could start sharing their pasts, with Naruto talking about his lonely childhood in Konoha and Samui sharing about her life in the Cloud Village. This sharing would bring them closer, and they might develop a deep friendship at first, which could potentially turn into something more romantic as they face more and more challenges together.
One possible plot could be that Naruto and Samui are on a mission outside Konoha when they receive some crucial information that puts Konoha in danger. However, they realize that there are traitors within the village who would stop them from using this information to save it. So, they decide to leave Konoha temporarily to gather more evidence and allies. Along their journey, they face various challenges and also start to understand each other better, with Naruto's determination rubbing off on Samui and Samui's calm and strategic thinking helping Naruto in different situations.
Sakura would probably be very worried. She has always cared about Naruto deep down, so she might be constantly trying to find a way to bring him back. Kakashi, on the other hand, would likely understand Naruto's reasons to some extent. He might be sad but also respect Naruto's decision. As for Sasuke, if he is in the village at the time, he could be conflicted. He and Naruto have a complex relationship, and Naruto's leaving might make him realize how much Naruto actually means to him.
One idea could be that as Naruto leaves Konoha, he encounters a powerful and ancient creature in the wild. In a battle with it, the extreme stress and need to survive unlocks his hidden bloodline. This new power could be related to some kind of elemental control that is unique to his clan, like a special form of wind manipulation that is far more powerful than what he had before.
One possible plot could be that Naruto leaves Konoha due to some misunderstanding. Maybe he feels unappreciated in his relationship with Sakura (Narusaku). He might go on a journey to find himself. Along the way, he could encounter new enemies and also make new friends who help him see things from a different perspective.
In this kind of fanfic, one possible scenario could be that Naruto leaves Konoha due to feeling misunderstood. Maybe he has been wrongly accused of something and decides that he can't stay in a place where people don't trust him.
It could be a rogue ninja from another village who has a vendetta against Naruto. This ninja might spread false rumors about Naruto in Konoha, which eventually leads to Naruto leaving. So, this ninja would be the main antagonist as he is the root cause of Naruto's departure.
She could be quite competitive with some of the Konoha ninjas in the Chunin Exams. However, she might also show respect for their skills. If there are group battles, she might be hesitant to fully trust Konoha ninjas at first, but as they prove themselves, she could become more collaborative. She might also exchange ninja knowledge with some of the more friendly Konoha ninjas.
One possible reason could be for Naruto's safety. Maybe she has to go on a dangerous mission and believes Konoha is the safest place for him. Another reason might be that she is forced by some powerful enemies who threaten Naruto's life if she doesn't leave him in Konoha.
Maybe he marries an OC (original character). The author of the fanfic could create a whole new character with unique qualities that attract Naruto during his time away from Konoha.