There are some. You could also try Archive of Our Own (AO3). It has a large collection of fanfictions, including those related to kouga and kagome. The tagging system on AO3 makes it easier to find specific types of stories, like if you want a story that's more focused on their romantic interactions or a story that's set in a particular part of the Inuyasha universe.
One common theme is the growth of their relationship. It shows how they go from initial distrust or confusion to deep love. Another theme is adventure. Since they are in a world full of demons and magic, they often go on quests together. Also, the theme of sacrifice can be seen, like when one of them is willing to risk their life for the other in a dangerous situation.
One common theme is the clash of different worlds. Kagome is from a more traditional Japanese - inspired world in Inuyasha, and Hades is from Greek mythology. So, the exploration of how their two very different cultures and powers interact is often seen.
Another theme is self - discovery. As they interact more closely in fanfictions, both kikyo and kagome often learn more about themselves. They might discover new aspects of their powers or their personalities through their relationship with each other.
A common theme is the clash of their different worlds. Loki is from the Marvel universe which is often high - tech and filled with superheroes, while Kagome is from a more traditional fantasy world. Their adjustment to each other's worlds can be a big part of the story.
One common theme is the exploration of their complex relationship. Given their history in the Inuyasha series, fanfictions often delve into how they might overcome their differences and jealousy. For example, some stories might have them teaming up against a common enemy and gradually developing a new understanding of each other.