One possibility is that it's a psychological exploration in the fanfiction. Kushina might be under some sort of dark magic or mind control that makes her want Naruto's body. This could lead to a complex story of Naruto having to fight against his own mother's possessed form while also trying to find a way to save her true self.
Perhaps the fanfiction could explore a scenario where Kushina's spirit is corrupted. And she believes that by taking over Naruto's body, she can rewrite the past mistakes in the ninja world. However, this is just speculation as this is a very unorthodox concept compared to the positive and family - oriented themes in the main Naruto storyline.
In such a fanfiction, it could be a really dark and twisted plot. Maybe Kushina was somehow resurrected in an abnormal state and has some wrong perception that Naruto's body can help her achieve a certain goal, like getting revenge on those who once wronged her. But this goes against her character in the original Naruto series as Kushina is a loving mother figure.
A simple plot could be that Kushina's spirit appears to Naruto and tells him about her wishes for him. He then sets out on a journey to fulfill those wishes, facing various challenges along the way. For example, he might have to battle an old enemy who is trying to stop him from achieving what Kushina wants.
Yes, it is. In the original Naruto story, Kushina is Naruto's mother and their relationship is based on love and protection. The idea of her wanting Naruto's body goes against this fundamental relationship and is very disturbing as it implies a perversion of the mother - son bond.
One possible plot development could be that Kushina's spirit somehow manages to break through the boundaries between the afterlife and the living world. She then tries to communicate with Naruto, perhaps through dreams at first. This could lead to Naruto starting to search for a way to bring her back permanently, involving him in some sort of ancient and dangerous ritual that he discovers in some long - forgotten scroll.
One possible plot development could be that Kushina uses her influence within the village to start a formal request for Naruto to be returned from the ANBU. She might gather support from other characters who also care about Naruto's well - being, like Iruka or Jiraiya. This could lead to a series of political discussions within the village leadership about the role of the ANBU and whether Naruto's skills are better utilized elsewhere.
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.
One possible plot could be that Naruto travels back in time. He then uses his knowledge of future events and his ninja skills to train Kushina. Maybe he helps her become an even more powerful kunoichi and also gives her advice on her relationship with Minato.
Perhaps in this fanfiction, Kushina as a pet is a secret only Naruto knows about. It could show how their bond is different from the normal mother - son relationship. For example, she might be able to communicate with Naruto in a special way that no one else can understand, and they go on adventures together around Konoha.
In such a fanfic, perhaps Kushina manages to break free from the afterlife's constraints. She could use some sort of ancient jutsu that allows her to return to the living world. Then, she starts her journey to find Naruto. Maybe she disguises herself as an ordinary traveler at first to observe Naruto from afar, seeing how he has grown and all the hardships he has faced. Once she reveals herself, Naruto is initially shocked but then filled with joy at the thought of having his mother back.
The plot could be that Kushina wants Naruto to reunite with his father. She could use her spiritual connection to Naruto to plant the idea in his mind. Naruto then embarks on a journey to find out more about his father, Minato. Along the way, he discovers secrets about the past, including how his parents really met and fell in love. This could also lead to him unlocking new powers related to his family lineage.
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.