Transformation is another theme. The person might be changed, either for the better or the worse, by their association with the demon. And also, the discovery of self. Both the demon and the person often learn more about themselves through their relationship, which is really interesting to explore in these types of fanfictions.
Love against all odds is also very common. Society in these fanfictions usually frowns upon a relationship between a demon and a human, so the two characters have to fight for their love. And then there's the theme of power imbalance. The demon often has more power, and how they use or don't use it in the relationship is an important aspect.
The theme of redemption can also be found. Sometimes the demon in the fanfiction is on a path to redemption because of the influence of the reader. It gives the story a deeper meaning. Also, there's the theme of mystery. Demons are mysterious by nature, and the fanfiction often plays on that, with the reader trying to figure out the demon's true motives and nature as the story progresses. This keeps the readers hooked.
One common theme is forbidden love. Since demons and angels are often seen as polar opposites in the lore, their relationship is considered taboo.
A common theme is power. The combination of Naruto's existing powers and the added demon - related powers often leads to a new level of strength. Another theme is identity. Naruto has to figure out how being associated with a demon affects who he is. For example, in some fanfictions, he might struggle with being seen as a monster because of the demon connection.
Love is a very common theme. The idea of two different beings, like Demon Kagome and Kurama, falling in love despite their differences. Another theme is the struggle between good and evil, as Kagome is often depicted as having a demon side and Kurama has his own moral code.
Redemption is also a big theme. Naruto's demon side may have caused some problems in the past, and he tries to redeem himself in Sasuke's eyes. This theme adds a lot of emotional depth to the relationship between the two characters.
Power dynamics is a very common theme. The demon queen usually has a great deal of power, and the slave has little or none at the start. Another theme is redemption. The slave might seek to redeem himself or be redeemed in the eyes of the demon queen. Also, loyalty often plays a big part, as the slave may show extraordinary loyalty to the demon queen.
One common theme is the power of friendship. Despite yami being a demon, they form a strong bond with yugi. Another theme is self - discovery. Yugi often discovers new aspects of himself through his relationship with yami.
A prevalent theme is the exploration of identity. The angel may question its own purity when in love with a demon, and vice versa for the demon. The lemon parts of the story add a layer of physical and emotional exploration, which ties into this theme of identity. In many of these fanfictions, the relationship is not just about physical attraction but also about how they redefine themselves through their love.
One common theme could be the struggle between the magical world of Harry Potter and the demonic elements. There might be a focus on the relationship dynamic between the Harry Potter characters and the demon characters, perhaps with themes of acceptance or conflict due to their different natures.
One common theme is power. Since Naruto is a demon and Kyuubi is a powerful being as well, the stories often revolve around how they use and control their powers. Another theme is partnership, showing how they work together.