One of the main themes is the relationship between the Duke of Death and his maid. It explores how they interact despite his rather unique 'curse' of killing anything he touches. Another theme could be about acceptance, as the maid seems to accept the Duke for who he is.
Well, generally in such a story, it might be about a girl who becomes a maid in the duke's family. There could be a lot of drama, like dealing with the strict rules of the household, the different personalities among the family members, and perhaps some secrets hidden within the family. Maybe she also has her own dreams and struggles while working there.
One thing that might make it unique is the concept of the duke of death. It's not a common character type. His relationship with the black maid is also a key factor. Their interactions could be different from the typical master - servant relationships in other stories.
Definitely the Duke of Death. His character is full of contradictions. He has this deadly power but also shows a vulnerable side, especially in his relationship with the maid. The maid is also fascinating. She is not afraid of the Duke's power and instead tries to understand him and be close to him. And there are some side characters as well, like the people who interact with the Duke and the maid from time to time, which add more depth to the story.
The maid is the central figure. The duke is a key character as well, his actions and decisions would greatly impact the maid's life. Besides, there could be a kind-hearted servant who befriends the maid, or a cruel head servant who makes her life difficult. The duke's heir, if there is one, could also be a main character, with his own ambitions and plans that might cross the maid's path.
Well, from the title 'sincerely i became a duke's maid web novel', it seems that the story is likely to revolve around a protagonist who, sincerely (maybe with genuine intentions), enters into the role of a maid in a duke's residence. This could lead to all sorts of plotlines. For example, she might face challenges in adapting to the strict rules of the duke's household. There could be rivalries among the servants, or she might find herself in the middle of some sort of drama involving the duke's family affairs. Maybe she has a secret past that she is trying to keep hidden while working there, and this secret could be a major driving force in the story.
Since I haven't read it, I can't say for sure. But I would assume the maid herself is a main character, and of course, the duke would likely be an important character as well.