Well, usually they might focus on the romantic or sexual relationship between Erwin and Levi. But since 'lemon' implies sexual content, it's not something that should be widely promoted. However, in non - lemon fics, characteristics could include exploring their different personalities, how they interact in the military setting, and their loyalty to each other.
One idea could be a story where Levi and Eren are on a dangerous mission together. They start off not getting along well due to their different personalities. Levi is strict and methodical while Eren is impulsive. But as the mission progresses, they gradually learn to understand and rely on each other. For example, Eren might save Levi from a Titan in a moment of quick thinking, and Levi in turn teaches Eren some crucial combat skills.
One aspect of Levi x Eren family fanfiction could be the exploration of their relationship in a family - like dynamic. It might involve how they support and protect each other within this new family structure. For example, Levi could be a strict but caring figure, while Eren is the one with new - found responsibilities in this family.
Female Eren in this fanfiction is often portrayed as headstrong. Just like her male counterpart, she has a strong sense of justice and is determined to fight for what she believes in. She is also likely to be brave, not afraid to face danger head - on, whether it's in battle or when confronting the complex relationship with Levi.
A third theme is sacrifice. Sometimes, Erwin has to sacrifice his own needs or wants in order to help Levi. This could be in terms of time, energy or even putting himself in danger. It shows the selfless nature of their relationship in these fanfictions.
In many Attack on Titan fanfics about Levi and Erwin, their relationship is often complex and deep. Levi respects Erwin's leadership skills and strategic mind. Erwin, on the other hand, trusts Levi's combat abilities. Their relationship can be seen as a partnership that is crucial for the Survey Corps. They support each other in the face of the Titans and the many challenges within the walls.
One popular trope is the 'unspoken understanding' between them. They can communicate with just a look during crucial moments in battle or decision - making. Another is the 'protective Levi' trope, where Levi is always ready to defend Erwin from any threat, whether it's a Titan or a political enemy within the walls.
In Levi x Erwin mpreg fanfiction, a frequent theme is the emotional journey. Erwin might struggle with his new role as a potential parent, and Levi has to support him through it. There's also the theme of secrecy and how they keep this from others in a world where such a thing might be seen as strange or unacceptable. It also often includes themes of sacrifice, as they might have to make difficult choices to protect their unborn child and each other. Additionally, the theme of family and what it means to them in this new situation is quite common.
It's hard to say. 'Levi x Eren' fanfics are quite common in certain fandoms, but the 'Levi is a criminal' aspect makes it a more specific and perhaps niche sub - genre. If there are a lot of fans who like to see dark or morally ambiguous takes on the characters, it could potentially be popular within that subset of the fandom. However, it also might not be mainstream popular as it goes against the more typical heroic portrayals of the characters.
There's also 'Eren's New Perspective'. In this fanfic, female Eren brings a fresh view to her relationship with Levi. It delves into how their different personalities clash and mesh. The story often has them facing challenges together and growing closer through shared experiences.