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.
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.
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.
Often, there are themes of adventure. Maybe they go on a journey together, facing various challenges in a world full of magic and mystery. This could be in the context of the Naruto universe or some alternate universe created by the fanfic writer.
Friendship is a common theme. They are often depicted as having a deep, unbreakable bond that goes beyond their differences. For example, in many fanfics, they support each other in battles.
One common theme is friendship. Despite their rocky start, Kurama and Naruto develop a deep friendship which is often explored in fanfics.
Another theme is personal growth. Through their relationship, both Sesshoumaru and Kagome usually grow as characters. Sesshoumaru might become more in touch with his emotions, while Kagome might become stronger in her powers. This mutual growth is often a central part of the story in many 'sesshoumaru x kagome fanfic'.
One common theme is the idea of 'opposites attract'. Sesshomaru is often portrayed as cold and aloof, while Kagome is warm and empathetic. Their different personalities coming together is a popular concept.
One common theme is the exploration of a forbidden love. Since Kagome has a connection with Inuyasha, her relationship with Koga is often seen as something that goes against the norm in the original story setting.
One common theme is the idea of redemption. Seshomaru, who is often seen as cold and aloof, might find redemption through his relationship with Kagome. Another theme is the power of love to bridge differences. Since they are from different worlds, their love can show how love can overcome those barriers.
Another theme is friendship. Some fanfics show that despite their differences, they can become friends. They learn from each other's experiences and grow as individuals. This often involves them sharing their knowledge of the spiritual world and the human world respectively.