One possible theme could be self - reliance. The title 'leave this to me' implies that the main character takes on challenges by themselves, suggesting a theme of being able to depend on one's own abilities.
Another theme might be responsibility. If someone is saying 'leave this to me', they are taking on the burden of a task, so the light novel could explore the idea of being responsible for various situations, whether it's in a relationship, a job, or in a more fantastical adventure setting. It could also deal with the growth that comes with taking on such responsibilities.
A third theme could be friendship or camaraderie. Maybe the main character initially says 'leave this to me' but then discovers that they need the help of their friends. So the story could be about how they balance their independent streak with the support and importance of their relationships with others.
In 'the hero proposed to me light novel', themes such as destiny or fate might be present. Maybe the story implies that they were meant to be together, and the proposal is a culmination of that. Additionally, the theme of courage could be there. It takes courage for the hero to propose, and perhaps the protagonist also has to be brave to accept or reject the proposal, which can explore different aspects of their personalities.
One possible theme could be redemption. As mentioned before, if a character has done wrong in the past, the idea of being brought into the light can symbolize their path to making amends.
Well, it could be about a person or a group who have some special mission or goal that demands they leave no trace. This could involve not leaving physical marks, like footprints or fingerprints, but also not leaving any social or emotional 'traces' in a more metaphorical sense. Maybe they are spies, or on a quest in a world where leaving a trace can bring unwanted consequences.
A theme of isolation might be explored as well. If the dead are rising, society could break down, leaving individuals or small groups isolated. This could lead to a sense of loneliness and the need to find new connections in a world full of danger. Additionally, there could be a theme of the unknown. The nature of the rising dead, why it's happening, all these are mysteries that could drive the story.
One possible theme could be adventure. If 'fenglingtianxia' implies a vast world or realm, the characters might embark on an adventure through this world, like exploring new lands or seeking treasures. And if 'wangfei' is involved, there could be a theme of royalty or court intrigue. The wangfei might be involved in political struggles within the court.
One possible theme could be friendship. Geniuses coming together often form strong bonds and support each other through various challenges.
One possible theme could be loneliness. Since it's about a deserted woman, she is likely to be alone and deal with the emotions that come with isolation. Another theme might be self - discovery. As she is in a difficult situation, she may start to find out more about herself and what she really wants.
Power and leadership could be a theme. Since it's about a 'cosmos ruler', it might explore how one gains, wields, and is affected by power in a vast universe.
Another theme might be self - discovery. The main character could go through a journey of understanding themselves better throughout the story, and the ending could be a culmination of this self - discovery. They might realize their true desires, values, or even their own strengths and weaknesses.
Since I haven't read it, it could be about friendship. Many light novels explore the deep bonds between characters, so it might be a theme in 'Five Days Light Novel'.