He could also go into a state of denial. Naruto has always believed in the good in people, especially his family. So, he might think that it's all a big mistake or that someone is forcing his mother to do this. He would then start investigating to find out the truth.
Naruto might also feel a sense of determination. He has faced many challenges in his life and has always come out stronger. This time, he would be determined to prove his innocence to his mother. He would use his skills and the bonds he has formed with his friends to try and clear his name. He would probably not fight back against Kushina directly at first but try to reason with her.
At first, Naruto would probably be extremely confused and hurt. He loves his mother and can't understand why she would do such a thing. He might try to find her immediately to talk it out.
Another reason might be related to some external influence. Suppose an enemy of the village has the power to manipulate Kushina's mind or emotions. They could make her target Naruto by making her see him as a threat to her or the village. In the Naruto universe, there are many powerful jutsu that can control people's thoughts.
At first, Naruto would be shocked and confused. His world view would be shattered. But then, he would draw on his inner strength. He has overcome so many hardships before. He might feel a deep sadness, but also a sense of resolve. He would still believe in the power of love and friendship, and use that to face Kushina's betrayal. He could also use this experience to grow even stronger and more determined to prove himself and his beliefs.
Naruto would probably be very confused at first. Kushina is his mother, so her hurting him would go against his understanding of their relationship. He might initially try to talk to her, to find out what's wrong and if there's a way to fix it.
Iruka would probably be one of the first to notice and try to step in. He has always been like a father figure to Naruto. He would likely confront Kushina and try to protect Naruto. Sasuke might be a bit more conflicted at first. He has his own issues, but seeing Naruto being abused, he would probably end up on Naruto's side and try to figure out what's wrong with Kushina.
Naruto would probably be really confused at first. He's used to a loving mother figure, not a yandere one. He might try to talk to her and understand why she's acting so strangely.
Naruto might first be in denial. He would find it hard to believe that his mother would break a promise to him. But as the truth sinks in, he could become angry. He might lash out, either physically or verbally, at those around him who remind him of the broken promise. Eventually, he would probably turn this pain into motivation to prove himself despite the setback.
They would be absolutely devastated. Minato, as Naruto's father, would likely be filled with guilt for not being there to protect him. Kushina, as his mother, would be heartbroken. They might first be in a state of shock, unable to believe what has happened. Minato might blame himself for leaving Naruto alone in a world full of dangers. Kushina would probably hold Naruto's body close, crying uncontrollably, and their grief could be so overwhelming that it would change the entire course of the ninja world they live in as their connection to Naruto was a major part of their lives.
Naruto would be heartbroken. He might initially be in denial, not believing that his mother could forget him. Then he would probably get angry, vowing to find out who or what caused this and make them pay. After that, he'd turn his anger into determination and start looking for solutions to bring back her memories.
At first, Naruto would likely be very confused and hurt. He has always craved family love and acceptance, so this sudden turn would be a huge blow. He might try to plead with his family, asking them to believe him and give him a chance to explain.
Minato might be intrigued. He would be interested in seeing how the fans expand on Naruto's journey. Kushina would be delighted, seeing her son as the center of so many different tales.