One possible aspect to analyze in a Kushina x Minato fanfic could be their relationship dynamics. Their love was strong and Minato was always very protective of Kushina. Fanfics might explore their courtship in more detail, like how they first fell for each other.
One possible reason could be a misunderstanding. Maybe Minato thought Kushina had done something to endanger Naruto when in fact she hadn't. In the heat of the moment, he lost his temper and slapped her.
In a fanfiction, if Minato were to slap Kushina, it would be a huge shock to the Naruto - Kushina relationship. It could potentially cause a rift between Naruto and his father Minato in Naruto's mind. Also, Kushina would likely be deeply hurt and angry, which might lead to her distancing herself from Minato. This event could also change the way Naruto views his family's past and his parents' relationship.
The theme of family also comes up a lot. Since they are the parents of Naruto, fanfics may explore how they would have been as a family. They might show Minato and Kushina preparing for Naruto's birth and their hopes and dreams for their son. Additionally, the theme of friendship is present as they have friends within the village who support their relationship.
One common theme is their love story. Writers often focus on how they fell in love, from their first encounters to the deepening of their relationship. Another theme could be their roles as parents. Since they are Naruto's parents, some fanfics explore how they would have raised Naruto if they had survived.
I'm not sure if there is such a fanfiction specifically. Fanfiction websites have a vast range of works, but 'lemon' fanfictions often contain inappropriate content. It's better to focus on non - explicit fanfictions that explore the relationships and stories in a more positive and appropriate way.
Another theme could be family. Since they are the parents of Naruto, fanfics might explore how they would have raised Naruto together. This includes their parenting styles and the values they would have instilled in him.
One idea could be that as Minato is dying, he passes on his special jutsu knowledge to Naruto in a final moment of father - son connection. Kushina, on the other hand, tries to comfort Naruto while also mourning Minato.
The theme of heroism also appears. Minato was a great Hokage and Kushina was a strong kunoichi. Fanfics may depict them facing various threats together, showing their heroic sides and how they supported each other in difficult situations.
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.