Maybe he goes into self - exile. After the Wave arc, he might feel that he's not strong enough yet and doesn't want to put his friends in danger, so he decides to disappear to train on his own.
Well, one reason could be that he's kidnapped by a secret organization. They might see his potential and want to use him for their own evil plans.
In some fanfics, it could be due to a time - travel related incident. He could accidentally be sent to another time or dimension during or after the Wave arc, which makes it seem like he has disappeared from his original world.
He could become more empathetic. After seeing the suffering in Wave, Naruto might be more in tune with the pain of others. So when he meets people in similar situations later, he can better understand their feelings.
One reason could be that he feels burdened by the expectations and the weight of his newfound peacekeeping role. He might want to escape the constant pressure and find himself. Another possibility is that he discovers a new threat during the post - war reconstruction and decides to go into hiding to investigate it without causing panic. Maybe he also has some personal issues related to his relationships, like feeling estranged from his friends who have changed after the war, and he needs time alone to sort things out.
One possible reason could be a sense of being undervalued. Maybe he felt that his teammates didn't fully appreciate his efforts during the Wave mission. For example, if Sasuke got most of the credit, Naruto might feel pushed aside.
One possible change is that she becomes more self - reliant. In the Wave arc, she saw the limitations of her own abilities. So in fanfictions, she might start to focus on self - improvement. Maybe she begins to practice her combat skills more rigorously, so that she can hold her own in battles without always depending on Sasuke or Naruto.
One reason could be the trauma he experienced during the Wave mission. He might have seen the darker side of the ninja world, like the cruelty of Zabuza and Haku's situation. This could have made him more guarded and seemingly cold as he realizes the harsh reality.
Well, one reason could be that he's on a secret mission for S.H.I.E.L.D. that requires him to go undercover and cut off all contact. Maybe he's investigating a new super - villain threat that's too dangerous to let anyone know about.
Well, in certain fanfictions, Naruto's view of the ninja world as a whole can shift after the Wave arc. He might start to question the traditional ninja values. Since he witnessed the greed and corruption that led to the problems in Wave, he could strive to change the ninja world from within. He may begin to form his own ideas about what it truly means to be a ninja, which could be different from what he was taught at the academy. He could try to promote peace and cooperation more actively, rather than just following orders blindly.
In 'naruto is betrayed in wave fanfic', it could be that Naruto is betrayed because of false accusations. People might believe that he's working with the enemy. His friends in the Wave mission, like Sasuke or Sakura, could turn their backs on him. They might not trust him anymore and even try to stop him from achieving his goals in the mission.
One possible reason could be that he is suffering from post - traumatic stress disorder. After all he has been through, he might want to isolate himself from the wizarding world to heal. Another reason could be that he feels a sense of guilt for those who died in the war, and disappearing is his way of punishing himself.
In some fanfictions, it could be due to a powerful emotional shock. Maybe seeing a friend in great danger at Wave, like Sasuke almost dying, could trigger an unexpected connection to the Sharingan. Since Naruto has a strong bond with Sasuke, this extreme situation might force his latent Uchiha - like powers (in the context of the fanfic) to surface, awakening the Sharingan.