One common theme is the exploration of the blurry line between friend and foe. Since the Female Titan is initially an enemy, fanfictions often delve into whether she can become an ally through her interactions with Armin. For example, Armin might try to convince her to side with the humans.
In the Attack on Titan manga, Armin is still alive. His character plays an important role and continues to be part of the story's progression. There are many close calls, but he manages to come out unscathed.
Another difference lies in the overall mood. Canon AOT has a rather dark, gritty, and often hopeless mood due to the constant threat of Titans. However, a friendly Titan fanfic would likely have a more positive, hopeful mood. It might explore themes of redemption for the Titans, or how their existence could be beneficial to the world of AOT. This is a complete departure from the doom - and - gloom feeling that often pervades the official AOT story.
Yes, there are quite a few. You can try searching on fanfic websites like Archive of Our Own. Just type in 'Female Titan x Armin' in the search bar and you'll get a list of relevant fanfics. Some might be really well - written with interesting plot twists and character developments.
One possible storyline could be that Armin discovers a way to communicate with the Female Titan on a more empathetic level. He tries to understand her motives beyond just being an enemy. Maybe she has some hidden knowledge about the Titans that Armin needs to save humanity.
One popular theme is the growth of their relationship. Starting from distrust or indifference and evolving into a deep friendship or something more. Another theme could be them facing challenges together, like a particularly difficult Titan attack where their combined skills are put to the test. Also, the theme of sacrifice might be present, where one is willing to sacrifice for the other in a life - or - death situation.
In Attack on Titan fanfiction, Armin and Levi often have an interesting relationship. Levi is the strong and stoic captain, while Armin is the intelligent strategist. Their interactions can range from mentor - mentee, where Levi imparts his combat and survival skills to Armin. Also, they might be comrades in arms, relying on each other during difficult battles. Their relationship can add more depth and complexity to the fan - created stories, exploring different aspects of their personalities as they face the challenges of the Titan - filled world together.
One popular trope is the 'enemies to lovers' dynamic. Given their positions as former enemies in the main story, it's common for fanfictions to explore how they transition from hostility to love. Another trope is the 'hurt/comfort' where, for example, Annie might be injured or in distress, and Armin is there to comfort her, which deepens their bond.