In this fanfiction, the plot might involve Kushina coming back to help Naruto in his toughest battles. Maybe she uses her unique chakra abilities that Naruto has inherited to give him an edge. She could also provide emotional support, as Naruto has always longed for his mother.
Obviously, Kushina is one of the main characters. Naruto is also a central figure as her son. Since it's related to the Naruto universe, characters like Sasuke, Sakura, Kakashi might also be important in the fanfiction. They could interact with Kushina in various ways, like Sasuke might be skeptical of her at first, or Sakura could be eager to learn from her.
She could also be amused in some cases. If the fanfiction has some really out - there but harmless ideas about Naruto, like him having a strange hobby that doesn't really change his fundamental good nature, Kushina might find it funny and just shake her head at the creativity of the fanfiction writer.
One possible plotline could be Kushina's reunion with Naruto and how she uses her skills and wisdom to help him in his battles. For example, she might teach him some new jutsu that only she knew. Another plotline could involve Kushina exploring the new ninja world that has changed so much since her time. She could interact with characters like Sasuke and Sakura, and have an impact on their development as well.
Sasuke might be affected as Naruto's closest friend. With Kushina back, Naruto could be more at peace, which might change the dynamic of their relationship. Sasuke could see a different side of Naruto, one that is more complete with his mother's presence.
Kushina returning to find crazy Naruto fanfiction could lead to a whole range of reactions. Firstly, she might be appalled at how some fans have twisted the story of her son. On the other hand, she could be amused by the wild ideas. If she finds fanfictions that involve her own backstory in strange ways, she might feel a bit violated but also intrigued. For instance, if there's a fanfiction where her relationship with Minato is completely different from what it really was, she'll have a strong reaction. But overall, it would be a very interesting encounter between her and the world of Naruto fanfiction.
She could be angry if the fanfiction distorts Naruto's character or the story in a negative way. For example, if Naruto is portrayed as a bad person in the fanfiction, Kushina, as his mother, would not like it at all. But if she finds some positive and creative fanfictions, she might be impressed by the fans' imagination.
Well, one scenario could be that Kushina finds a fanfiction where Naruto has turned evil due to some dark force. Another might be that she discovers a story where Naruto is in a relationship that is completely out of character for him. Maybe she stumbles upon a fanfiction where Naruto has some really strange and overpowered abilities that don't fit the original Naruto universe.
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.
Naruto would be overjoyed to see his parents. Emotionally, it would give him a great boost. He would finally have the family he always dreamed of having around him.