One of the popular themes could be the struggle between good and evil. The Night Prince might face various antagonists that represent different forms of evil, and his journey to overcome them is a central aspect.
Power and its consequences could be another theme. As a prince, he may have a certain amount of power, and the novels might explore how he uses it, whether for the good of his people or for his own gain, and the moral implications that come with it.
One popular theme is competition. Combining the competitive nature of tennis from Prince of Tennis with the battles in Naruto. Another is friendship, as characters from both series form new bonds.
One of the most popular themes is the exploration of different character relationships. For example, the relationship between Shirou and Saber is often delved into more deeply in fanfiction, showing different possible scenarios and emotions. Another common theme is alternate universes, where the story takes place in a different setting or with different rules, which can bring a whole new perspective to the Fate Stay Night world.
A common theme is redemption. Writers often explore the idea that the Night Queen could be redeemed, perhaps through some self - sacrifice or by finding a way to break the curse that made her what she is. Another theme is her power. Many fanfictions focus on how powerful she really is and how she could use that power differently.
I think 'The First Heretic' is very popular. It has a complex plot that involves the fall of the Night Lords legion from their original state. It also has great character development for the main characters within the Night Lords.
A lot of Crown Prince Harry Potter fanfictions explore the theme of cultural exchange. The Crown Prince brings the traditions and values of his own royal culture into the wizarding world. This can lead to some interesting scenarios, like new magical practices being introduced, or different social norms being challenged. There are also fanfictions that focus on the Crown Prince being a catalyst for change in the wizarding world. Maybe he helps to modernize Hogwarts or reform some of the old - fashioned wizarding laws, all while interacting with Harry Potter and other key characters.
One popular theme is character crossovers. People love to see how characters like Shirou from 'Fate Stay Night' would interact with Harry Potter. Another theme is magic system combinations. Combining the magecraft of 'Fate Stay Night' with the magic of 'Harry Potter' can lead to really cool and unique story elements.
Love and Romance. There are often complex relationships between the characters, especially between the human and vampire characters.
Romance is likely to be a main theme. Since it's a 'night prince', there may be some sort of love story involved, perhaps between a human and the prince.
Love and marriage are very popular themes. In Austen's novels, like 'Pride and Prejudice', the relationship between Elizabeth and Darcy shows how love can develop and overcome initial prejudices. Social class also plays a big role. Characters' status and wealth often influence their marriage prospects and social interactions.
Social and political issues are also popular themes. For example, in 'Animal Farm', it's about the corruption of power in a political system. Novels in the top 25 often use their stories to comment on the real - world social and political situations.