It depends on the nature of the fanfiction. If it adheres to the general rules of respect and propriety, and doesn't involve inappropriate or offensive content, it can be an acceptable form of creative expression within the fan community.
One key element is the exploration of their different personalities. Camilla is often depicted as strong - willed and protective, while Corrin is more idealistic. Their interactions based on these traits form a big part of the fanfiction.
One common theme is loyalty. Given their relationship in the source material, loyalty to each other often plays a big part in fanfiction. Another theme could be protection, with either Corrin or Camilla being very protective of the other.
One popular theme is loyalty. Given their connection in the game, fanfics often explore how loyal they are to each other. Whether it's facing external threats or internal conflicts within their group, their loyalty is put to the test.
The fanfiction often delves into their backstories and how it affects their relationship. Corrin's journey and Camilla's past experiences can be intertwined in these stories. It could be that Corrin's growth as a character is influenced by Camilla, and vice versa. This mutual influence can be a central theme in many Fire Emblem Corrin x Camilla fanfictions.
One good theme could be redemption. Maybe Corrin has made some mistakes and Camilla helps him/her to find a way to make up for it. Or a theme of discovery, where they discover new aspects of each other's personalities and cultures. It could also be a theme of protection, with Camilla protecting Corrin from a powerful enemy, which strengthens their connection.
You can try looking on some popular fanfic websites like Archive of Our Own (AO3). There are often a wide variety of fanfics for different pairings, and it's likely that you'll find some for Female Corrin x Camilla there.
One common theme is loyalty. Camilla and Corrin often show deep loyalty to each other in these fanfics. Another theme is sacrifice, as they might be willing to give up things for the other's sake.
One popular camilla x corrin fanfiction is 'The Bond Beyond Kingdoms'. It beautifully explores their relationship in a post - war scenario where they work together to rebuild their lands and in the process, their feelings for each other deepen. The story is filled with emotional moments and great character development.
One common theme is friendship. They might explore how female Corrin and Camilla become friends and support each other through various challenges in the Fire Emblem world.