There are various types of Saito and Louise married fanfiction. Some are light - hearted and focus on the comical situations that might arise from their different cultural backgrounds (since Saito is from a different world). Others can be more serious and delve into the deeper emotional bonds between them. The fanfiction can also explore how their marriage affects the political and social aspects of the world they live in, as Louise is a noble and Saito has his own unique position in that world.
In fanfics, Louise is often depicted as a strong - willed and sometimes temperamental character. She has her own insecurities, especially when it comes to her magical abilities. Saito, on the other hand, is usually portrayed as brave and loyal. He comes from a different world, which adds an interesting dynamic to their relationship as he has to adapt to Louise's world of magic.
In fanfiction, the idea of Saito and Louise being pregnant often adds a new dimension to their relationship. It could be a way to explore their growth as characters. Maybe it shows their transition into a more mature phase of their relationship, with the responsibilities of impending parenthood.