Naruto could also feel a deep sense of hurt. After all, he has been through a lot with Sakura. In the face of her betrayal, he might start to question his own judgment of people. However, being Naruto, he would not give up easily. He might try to find a way to redeem Sakura or at least make her see the error of her ways. He would draw on his own experiences of being ostracized in the past and use that to try to understand her actions and find a solution.
It often changes drastically. Sakura may initially feel hurt and angry. She might start to question all her previous beliefs about Naruto. For example, if Naruto betrays her trust in a battle situation by seemingly siding with the enemy, Sakura's view of him as a reliable friend and teammate would be shattered.
One possible scenario could be Naruto being forced into a situation where he has to seem to betray Sakura to protect her from a greater danger. For example, he might be blackmailed by an enemy into staying away from her or acting against her interests.
In some fanfiction concepts, Sasuke might betray Naruto due to his unwavering pursuit of power and a different view of the ninja world. Sakura could be involved perhaps out of misguided loyalty to Sasuke. It could start with Sasuke believing Naruto is a hindrance to his goals and Sakura following Sasuke's lead, breaking Naruto's trust.
The consequences would be far - reaching. Naruto, being the optimistic and friendly character he is, would be deeply hurt. His power might be affected as his emotional state is in turmoil. He could also start to view the ninja world in a different light, seeing it as a place where even the closest friends can turn on you. This could lead to him making different choices in his battles and relationships, and may even push him towards a darker path himself in some fanfiction interpretations.
In some fanfictions, it could be due to a power imbalance. If Sakura gains a significant amount of power and her views change, she might see Naruto as a threat to her newfound status or goals. She could then betray him to secure her own position. Another aspect could be a love triangle gone wrong. If there's a third character involved in a romantic situation with either Naruto or Sakura, it could lead to jealousy and ultimately betrayal.
The betrayal could lead to Naruto having trust issues not only with Sakura but also with others in the future. He might become more guarded and less likely to open up to people. For Sakura, if she comes to her senses later, she would have to face the enormity of what she has done. She would have to grovel for Naruto's forgiveness, but it would be a long and difficult road to regain his trust.
He could be betrayed by a false friend in the DxD world who spreads lies about him. For instance, telling others that Naruto has a hidden agenda to take over their realm.
Another plot could involve jealousy. If Sakura becomes jealous of Naruto's growing popularity and power among the villagers, she might betray him. She could spread false rumors about him, which would lead to the villagers turning against Naruto.
Another plot could involve a love - related betrayal. Suppose Sakura is in love with someone who is an enemy of her village in secret. To protect this person, she betrays her village's secrets. It could create a lot of drama as her friends discover her actions.