Another possibility could be a new character. For example, a foreign ninja who has different skills and a unique personality. She could meet Naruto during his travels, and they could share a deep connection based on mutual respect and admiration for each other's abilities. This could lead to them falling in love and getting married.
One possible storyline could be that Naruto leaves Konoha to explore the world and on his journey, he meets a kind - hearted and strong - willed woman. They fall in love gradually as they face various challenges together. Eventually, they decide to get married. Maybe they have a simple ceremony with friends from his travels and old friends from Konoha coming to celebrate.
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.
Another possibility is that Naruto marries a completely new character. This character could be from a far - off land that Naruto visits during his departure from Konoha. She could be a powerful ninja in her own right, with unique abilities and a personality that attracts Naruto, leading to their marriage.
In this fanfic, Naruto might leave Konoha to protect his loved ones from potential threats in the village. When he gets married, it could be to a character like Hinata. They might start a new life in a peaceful place, away from the chaos of ninja battles. Maybe Naruto will teach his children the values he learned on his own journey.
He could feel a sense of guilt. Sasuke might think that his actions or their relationship issues pushed Naruto to leave. He may then set out to find Naruto, not only to bring him back but also to resolve their long - standing issues. For example, if there were unspoken words or unresolved fights between them, Sasuke would see this as an opportunity to set things right.
Naruto might encounter a group of rogue ninjas. At first, they seem like enemies, but as he gets to know them, he realizes they have their own reasons for being outcasts. They could teach Naruto some unorthodox fighting styles that are not taught in the Leaf Village. Also, there could be a mysterious traveler who has knowledge about Naruto's family that even he doesn't know. This traveler could be the key to unlocking some hidden power within Naruto.
Well, Naruto could leave the village in a fanfic due to a prophecy. He might believe that leaving is the only way to fulfill a greater destiny that the village can't support. As he leaves, he starts to explore different cultures of the ninja world. He learns about new forms of jutsu and how other villages operate. He could also form a team with outcasts from different villages, and together they strive to change the way the ninja world views things.
In the sasunaru context, perhaps a rift between Sasuke and Naruto makes Naruto feel like he needs to leave to sort out his feelings. He might think that staying in the village constantly reminded of Sasuke and their complicated relationship is too much to bear, so he leaves to find his own path and hopefully reconcile with Sasuke on his own terms.
Definitely Naruto and Sasuke. Naruto is the one leaving the village, so he's a central figure. Sasuke, given the 'narusasu' aspect, is bound to play a crucial role too. He could be the one Naruto is leaving behind, or he could be the one who follows Naruto out of the village. There might also be other supporting characters from the Naruto universe like Kakashi or Sakura who could be affected by Naruto's departure.