One possible reason could be some sort of dark force influencing Kushina's mind. Maybe she was under a powerful genjutsu that made her think she had to abandon Naruto for his own safety, even though it was a false perception.
I'm not sure specifically as there could be many different plots in such a fanfiction. It might involve Naruto having some god - like powers but being rejected or abandoned by his mother Kushina for various reasons, perhaps due to fear of his power or some dark influence.
Well, in such a fanfiction, Naruto might initially be filled with anger and confusion. He may have a harder time connecting with his peers in the village. As he gets older, he could start to piece together the events that led to Kushina's abandonment. Maybe there was some dark force or misunderstanding that caused it. This could lead to a whole series of adventures where he tries to set things right or find a new family in the form of his friends and mentors.
The fanfiction would also change the relationship dynamics in the story. For instance, Naruto's relationship with his father Minato would be more complex as he might also feel some resentment towards Minato for not preventing Kushina from leaving. It could also affect how Naruto views family in general, making him more cynical or desperate for family love.
The main characters are Naruto, who is in a rather tragic situation with his godlike abilities yet being abandoned. And Kushina, whose actions of abandonment drive the story forward. There might also be other characters like Naruto's friends or other ninja from the village who could play roles in how Naruto copes with the abandonment and his journey with his powers.
Naruto would likely become more self - reliant. Without Kushina's presence, he'd have to figure things out on his own more often. He might be a bit more withdrawn at first, but as he faces challenges, he'd grow stronger. His determination would be even more intense as he tries to prove that he can succeed without a mother figure.
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.
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.
One common plot is Kushina finding Naruto in a different time or dimension. For example, she might end up in the future where Naruto has grown up and she gets to see the kind of person he has become. It's an emotional and interesting concept as she gets to witness all his achievements and the challenges he has overcome.