Kushina's reaction could be complex. At first, she might be in disbelief, thinking it's some kind of mistake. But as the reality sinks in, she'll become extremely worried. She'll likely gather all her strength and determination to find Naruto. She may also think back to any threats or warnings that could be related to his disappearance and start formulating a plan to get him back.
She might be devastated. She could break down in tears immediately.
Kushina would most likely go into a panic. She'll start running around, calling out Naruto's name and looking in all the places he usually goes. She'll be in a total frenzy as Naruto is so important to her.
In the fanfic, when Kushina realizes Naruto is gone, she might first be in a state of shock. She could then start searching everywhere for him, frantically asking people if they've seen him. Maybe she'll recall their last moments together and feel a deep sense of regret for not being more careful with him.
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.
She might be shocked at first. Harley Quinn has her own view of Batman and Bruce Wayne, and realizing they are the same person would turn her world upside down.
She might be overjoyed. After all, Naruto is her son. She could immediately rush to find him and embrace him tightly, tears of happiness streaming down her face.
Naruto might be extremely heartbroken. He has always looked up to his mother, and being disowned by her would be a huge blow. He could become withdrawn and start to question his own worth.
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.
Kushina would be extremely worried. She would rush to Naruto's side immediately and start using her medical knowledge or any available resources to help him get better.
She would likely be devastated. Kushina has a deep connection to Naruto as his mother. She might first go into denial, unable to accept that her son is gone. Then, she would probably be filled with intense grief and anger. She could potentially lash out at those she blames for his death or just break down completely, mourning all the things Naruto could have been and all the time they missed when he was growing up.
He might be initially confused. Naruto is a character full of energy and he would probably just start blabbing about how he is a boy, not a girl. He could get a bit frustrated as well because Naruto doesn't like being misunderstood.
Naruto might initially be in shock. He has always idolized his mother, so if she suddenly hurts him, he would be completely taken aback. He might freeze for a moment, unable to believe what is happening.