It's possible that Kushina would rely on her own power and determination. She could track Naruto down by following his chakra signature. Once she finds him, she would have to break through any barriers, whether they be physical or emotional, that are keeping them apart.
Kushina could also seek the help of other powerful shinobi. For instance, she might ask Minato for assistance. Since Minato was Naruto's father and also a very skilled ninja, together they could come up with a plan to reunite with Naruto. Maybe they would use some sort of space - time ninjutsu to get closer to him.
She might start by using her knowledge of Naruto's past. Since she is his mother, she knows things about his early life that no one else does. She could use these memories to create an emotional connection with him. Maybe she'll show up in his dreams first, like a hazy memory, and then gradually reveal herself in the real world.
Naruto's reaction could be complex. On one hand, he would be extremely excited. But on the other hand, he would be worried about the consequences. He has learned about the balance of the ninja world and might be afraid that bringing Kushina back could have negative impacts. However, his love for his mother would probably overpower those concerns in the end, and he would still strive to make her return a reality.
In certain fanfic ideas, Naruto could have made a deal with some sort of otherworldly being. He might have sacrificed something of great value, like a part of his own chakra or a future ability, in exchange for Kushina's life. Another possibility is that he finds a way to reverse the very nature of death by using some unique properties of the tailed beasts' chakra that he has access to.
In a fanfiction, Kushina could want Naruto to master a unique jutsu that she had always dreamed of but was unable to achieve herself. This could be a jutsu that combines the power of the Uzumaki clan's sealing techniques with some other element, like wind. And she would be guiding Naruto in his journey to master it, through some kind of spiritual connection.
In certain fanfic concepts, Naruto could have found a special relic or artifact. This relic might have the power to reverse death. Since Naruto is always on adventures and exploring different places, he might stumble upon such an item and use it to revive Kushina. It could also be related to the Uzumaki clan's secrets that he uncovers which enables him to bring his mother back.
Another aspect could be the emotional impact on Naruto. Having his mother back would be a huge boost to his mental state. He's always longed for family, and Kushina's return would fill that void. It could change his perspective on life and make him even more determined to protect the village and his loved ones.
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.
The comfort from Kushina in the fanfiction might also inspire Naruto to be a better person. He might strive to live up to the values his mother represents, like kindness and perseverance. Her presence in his life, even if just in the fanfiction, can be a guiding force for him, making him more determined to protect those he loves and make the world a better place.
One consequence could be that it messes with the natural balance of the ninja world. Maybe the cycle of life and death is disrupted, and this causes some strange phenomena to occur, like abnormal weather or chakra imbalances.
Well, in some fanfictions, Minato might use his powerful jutsu to break through the barriers between the living and the dead and directly reach Naruto. He could also try to influence the people around Naruto to bring him closer to where Minato is, like using his spirit to communicate with Naruto's friends and convince them to help.