In fanfiction, this could be due to an alternate reality or a dark twist in the plot. Maybe Kushina was mind - controlled by some powerful enemy. It's a very strange and dark concept that goes against the normal Naruto storyline where Kushina is Naruto's mother and loves him dearly.
If Naruto were killed by Kushina in a fanfiction, it would completely shatter the Naruto universe as we know it. Naruto is the main character, and his death would mean the end of his journey to become Hokage and bring peace. All the relationships he had built, like with Sasuke, Sakura, and his other friends, would be left in ruins. It would also mean that the prophecy about him might not be fulfilled, leading to a darker and more chaotic future for the Hidden Leaf Village.
The most obvious consequence would be the extreme grief among Naruto's friends like Sasuke, Sakura, and Kakashi. They would be devastated and likely seek revenge. The village would also be in chaos as Naruto was seen as a hero - in - the - making. It would completely change the future of the village.
Another aspect could be that the fanfiction delves into how Kushina's presence affects Naruto's relationships with others. For instance, his relationship with Sasuke could be different. With a strong maternal figure in his life, Naruto might be more stable emotionally and be able to approach Sasuke in a more understanding way, which could potentially change the whole dynamic of their rivalry and friendship.
Well, for one, Hinata would be completely devastated. She loved Naruto deeply. Her world would crumble. Shikamaru, who respected Naruto's determination, would be angry and confused. Why would Kushina do such a thing? The other Konoha 11 members would also be in a state of disbelief. They had all fought alongside Naruto. Iruka, Naruto's first teacher, would be inconsolable. He had always believed in Naruto and watched him grow. And Jiraiya, if he were still alive in this fanfiction, would be filled with regret for not teaching Naruto more to avoid such a fate.
One possible fanfiction could be about Kushina finding Naruto in a situation where he's lost in a forest. Maybe she uses her unique chakra sensing abilities to track him down. It could be a heartwarming story of a mother reuniting with her son.
Minato could be a common character. Since he was Kushina's husband in the original story, his presence might add some interesting dynamics to the harem scenario. Another could be Jiraiya. His connection to Naruto and his reputation as a bit of a ladies' man could make for an interesting addition to the story.
One possible reason could be for Naruto's protection. Maybe she thought by banishing him from a certain place or situation, she could keep him away from a hidden danger that she knew about. For example, there might be a powerful enemy targeting Naruto specifically, and she believed that by making him leave, he would be harder to find.
Perhaps Naruto finds a way to travel back in time and prevent Kushina's death in the first place. He could use his Sage Mode or some other special ability to manipulate time. And then, by changing the past, he effectively'revives' her in the present. In the Naruto universe, there are all kinds of crazy powers, so time - travel isn't completely out of the question.
In some fanfictions, Kushina was sealed into Naruto through a complex jutsu. It might be a modified version of the sealing jutsu used to seal the Nine - Tails. The process could involve special incantations and chakra manipulations.