Power and its implications are often explored. Since both characters have some form of power, how they use it in relation to each other and in their relationship is a theme. For example, Kurama's fox - demon powers and Kagome's demon - influenced abilities. Also, redemption can be a theme, especially if Kagome is seen as a demon who needs to find her place in the world.
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.
Love and friendship are common themes. Since they are from different worlds in the original series, exploring how they form a bond, whether it's a romantic relationship or a deep friendship, is often seen.
One common theme is the exploration of their relationship. Since they are from different anime/manga universes, fanfics often deal with how they meet and interact in a crossover scenario.
One popular Demon Kagome x Kurama fanfiction is 'The Unlikely Bond'. It beautifully weaves their characters together in a world filled with magic and mystery. The author does a great job of showing how their different personalities complement each other.
The fanfiction may introduce new villains or threats that only their combined powers can defeat. This creates an interesting dynamic as they learn to work together. There could also be a lot of cultural exchange in the stories, as Kagome represents human values from her time period and Kurama has his own demon - based culture.
In 'Kagome is a dragon demon' fanfiction, themes often revolve around the transformation's consequences. For instance, there could be a theme of isolation. People might be afraid of her new form and keep their distance, which makes Kagome feel alone. Another theme could be adaptation. She has to learn how to use her new dragon - demon abilities, like flying or breathing fire if that's part of the concept. And of course, there's the overarching theme of how this change affects the story's world. Does it tip the balance of power? Are there new enemies or allies because of her transformation?
A common theme is the clash of two different worlds. Kurama being a demon and the human coming from a completely different realm. Another theme is acceptance. The human has to accept Kurama's true nature and Kurama has to understand human emotions and values.
One common theme is the power dynamic. Kurama is a powerful character, so exploring how his power interacts with the oc's abilities or lack thereof can be interesting. For example, he might protect the oc from other threats in the demon world.
Adventure is another theme. They might go on quests together, facing various challenges and monsters. This gives the writers a chance to show off their creativity in creating new worlds and scenarios for the characters. Also, the theme of self - discovery can be present. As they interact, they might learn more about themselves and their own powers.
One common theme is friendship. Since they come from different backgrounds in the original story, fanfictions often explore how they form a deep bond of friendship. For example, they might have to overcome misunderstandings about each other's powers or motives.
There are quite a few. You can check out some popular fanfiction platforms like FanFiction.net or Archive of Our Own. Just search for 'kurama x kagome' on those sites and you'll find a variety of stories with different plotlines and writing styles.