The theme of redemption also pops up often. Sadao Maou may be seen as a 'bad' character initially, but through his relationship with the OC, he may start to show signs of redemption. The OC might inspire him to make different choices, and this exploration of his character's potential for good is a recurring element in these fanfics.
Well, in 'evil Sadao Maou x reader fanfic', a frequent theme is the struggle between good and evil within the relationship. The reader may be a force for good trying to change Maou's evil ways. Also, themes of loyalty and betrayal can be present. Maou's actions as an 'evil' character might lead to situations where the reader has to decide whether to stay loyal or turn away. And sometimes, there's the theme of forbidden love, as being associated with an 'evil' character like Maou can be seen as something taboo in the story's context.
I'm sorry I can't directly recommend specific 'evil Sadao Maou x reader fanfic' as it depends on various fanfiction platforms. You could try searching on popular platforms like Archive of Our Own (AO3). There might be a lot of works there that fit this category.
One popular 'yandere Sadao Maou x reader fanfic' might be found on fanfiction.net. You can search there using the relevant tags. However, the availability and popularity can vary.
First, create conflict. For example, Maou's dark nature could lead to situations where he accidentally endangers the reader. This builds tension. Then, develop their relationship gradually. Don't rush into love. Let them learn about each other's quirks and secrets over time. Also, introduce side characters that either support or oppose their relationship. This adds more complexity. For instance, other dark beings who don't like Maou getting close to a human reader.
Common themes often include trust. Given Maou's dark side, it takes time for the reader to trust him and vice versa. There's also the theme of discovery. The reader gets to discover the different layers of Maou's personality. For example, beneath his dark exterior, there could be a more vulnerable side. And the theme of sacrifice might be present. Maou might have to sacrifice some of his dark desires or power for the sake of the relationship with the reader, or the reader might sacrifice something for Maou.
Well, 'OC's Impact on Maou's Realm' is another one. In this fanfic, the OC has unique abilities that disrupt and also improve Maou's world. It's an exciting read as it shows how the OC's presence affects the existing characters and the overall story arc in the world of Sadao Maou.
One main theme is the clash of different worlds. Maou is from a different realm and now has to exist in the modern world with Chiho. Another theme is friendship or relationship building. Chiho and Maou develop a special bond throughout the story.
Since I haven't actually read a specific 'maou and chiho lemon fanfic', it's hard to say exactly. But generally, it might involve some romantic or tense interactions between Maou and Chiho with some added elements of drama or adventure.