It could start with distrust. Saber Alter is different from the original Saber, and Shirou might be cautious. But as they face challenges together in Camelot, like battles against dark creatures, they start to rely on each other. This gradually builds respect and then a deeper connection.
You can start by looking on fanfiction.net. It has a large collection of Fate - related fanfictions, and you're likely to find some good ones about Shirou Kotomine and Saber Alter there. Just use the search function and type in the relevant keywords.
Another interesting one is 'Under the Moonlit Alter'. This story focuses on the more emotional side of their relationship. It shows how their bond develops over time, starting from a place of mutual suspicion to a deep and abiding connection. The author does a great job of describing their internal thoughts and feelings as they navigate their relationship.
One idea could be Shirou trying to understand Saber Alter's dark past in Camelot. He might discover the events that led to her becoming Alter. Another could be them teaming up to face a new threat in Camelot that neither could handle alone. Maybe a powerful mage is trying to rewrite the history of Camelot and they have to stop it.
The unique character design of Mysterious Heroine X Alter is a big draw. Her edgy and mysterious nature gives fanfiction writers a lot to work with. They can explore her backstory, her relationships with other characters in the Fate universe in really interesting ways.
Some Tumblr blogs are dedicated to Fate fanfictions as well. You can use Tumblr's search function to look for Mysterious Heroine X Alter fanfictions. But keep in mind that the content on Tumblr can be a bit unorganized compared to the more dedicated fanfiction platforms. You may need to spend some time exploring different blogs and tags to find what you're looking for.
One unique feature is the combination of different universes. For example, when Saber is crossed over with a modern - day setting, it creates a contrast between her medieval values and the contemporary world. This leads to interesting character development as she has to adapt.
One common theme is friendship. Despite their different origins and personalities, Rin and Saber often develop a deep friendship in these fanfics. They learn to rely on each other and support one another through difficult times.
😋I recommend to you "Saving the World with Fate's Power." The protagonist is based on Gilgamesh in the anime of the same name. Through inheritance, he has Excalibur and other powerful powers, leading the female protagonist Saber to save the world. "I'm done with the recommendation. I hope you like my recommendation. Muah ~"😗
One popular 'fate stay night saber crossover fanfiction' is 'Saber in the Modern World'. It's an interesting take where Saber is transported to the modern era and has to adapt to new technologies and social norms. Another one could be 'Saber and the Magic Academy Crossover'. In this, Saber enters a magic academy from another universe and has to deal with different magic systems and rivalries.