A common theme is the relationship between Emi and Maou. Whether it's a slow - burn romance or a more platonic friendship evolving, it's often explored.
Another theme is the adaptation to the human world. Since they are from different realms, how they continue to deal with human society and its norms while being who they are is often in these fanfictions.
Power dynamics also play a role. Given that Emi is an enemy of Maou in the original story to some extent, how their powers interact and change in different scenarios in fanfiction, like in battles or when they are forced to cooperate, is a frequent theme.
Another way is by exploring their pasts. Maybe they discover that they have more in common than they thought in terms of their upbringing in their respective worlds. This newfound knowledge can make them more empathetic towards each other. For instance, if they find out that they both had a mentor figure who had a big impact on their lives, it could create a bond.
The appeal often lies in the relationship between Maou and Emi. Their dynamic, being from opposite sides originally, is very interesting.
Their relationship can be developed through shared experiences. For example, if they go on a mission together to save a human from a demon's curse. During this mission, they would have to rely on each other, communicate more, and understand each other's strengths and weaknesses better. This would bring them closer and deepen their relationship.
One idea could be that Maou and Emi have to team up to face a new, more powerful demon from Maou's past. This demon challenges Maou's leadership and Emi realizes she has to help him to keep the peace in their current world.
A prevalent theme is adaptation. The devil has to adapt to the human world in order to survive, and Emi also has to adapt to co - existing with him. Also, the theme of redemption can be seen sometimes. Maybe the devil starts to do good things in the human world, which is a form of redemption for his past actions in their demon world.
One great fanfiction could be 'The Unlikely Alliance' where Emi and Maou have to team up in a different way than in the original story to face a new threat. It has really interesting character development.
One popular fanfiction might be 'Maou and Emi's New Adventure' where they face a new threat in the human world together. It's full of their typical banter and some sweet moments.
One common theme is loyalty. Ashiya is always loyal to Maou in the series and fanfictions often explore this aspect further, showing how their loyalty to each other helps them face various challenges.
One idea could be that Emi and Maou have to team up against a new threat in the human world that is more powerful than any they've faced before. Maybe a powerful demon from the other world has found a way to cross over and is causing chaos, forcing Emi and Maou to put aside their differences and use their combined powers to stop it.
The theme of power dynamics between them is also quite popular. Given that Sadao is a demon and Emi is an angel, their different powers and how they interact with each other in various situations, such as in battles or when they are forced to cooperate, are often explored in fanfiction.