Maybe out of curiosity. They want to see how the fans view Kakashi, who was an important part of their lives. Kakashi was Minato's student and Kushina knew him well too. So they are interested in the different perspectives presented in the fanfiction.
They might be quite surprised. Minato might be proud to see how much Kakashi has grown in the fanfiction and how he is still upholding the values Minato instilled in him. Kushina could be amused at the creative interpretations of Kakashi's character. Maybe she would also feel a bit of motherly pride seeing how Kakashi has become an important figure in the village in these fictional stories.
Minato would likely create some special seals to protect Naruto. These seals could be placed on Naruto's crib or on his clothes. They would act as a sort of early warning system or even a shield in case of an attack. Kushina would use her maternal instincts to sense any danger coming. She would be constantly on guard, and if anyone tried to harm Naruto, she would not hesitate to use her chakra chains and her Uzumaki - level combat skills to fight them off. Also, they would educate Naruto about the importance of self - defense from a very young age, so that he could protect himself when they weren't around.
On a more personal level, they could face internal guilt. As Naruto grows up and achieves great things on his own despite their neglect, Minato and Kushina may realize what they've missed out on. This realization could cause them a great deal of internal turmoil and regret for not being there for their son when he needed them.
Minato would probably be very proud. He might notice Naruto's use of his own jutsu and be impressed by how Naruto has developed his skills. Kushina would be more emotional, maybe crying at the sight of Naruto growing up so well.
Well, in some fanfictions, the moment when Minato sacrifices himself to save the village while Kushina is already dead is extremely emotional. It shows his selflessness and also the love he has for the village and his family. Also, the flashbacks in some stories about their early days together, like when they trained together as young ninjas and slowly fell in love, are really sweet and emotional.
It might be due to jealousy. If Minato was getting more attention or praise in the village for his achievements while Kushina felt overlooked, that could create resentment. Say, Minato was constantly being hailed as a hero for his speed and battle tactics, and Kushina, who also had great power, felt like she was in his shadow.
At first, Naruto and Kushina might start to distance themselves from Minato. They could avoid him and not talk to him as much. As time goes on, the hatred might grow deeper. Naruto could start to oppose Minato in public or in important village matters. Kushina might also try to influence others in the village against Minato.
No. In the Naruto series, Minato and Kushina have a loving relationship. A fanfiction depicting abuse goes against the essence of their characters and is inappropriate.
A fanfiction could explore the backstories of these characters more deeply. For instance, how Mikoto came to be so proficient with her sharingan, and how her friendship with Minato and Kushina developed over time. This could add a lot of depth to the existing Naruto lore.