Well, a very prevalent theme is the exploration of their different personalities coming together. Kagome is often portrayed as kind - hearted and strong - willed, while Kouga is more wild and free - spirited. Fanfics might focus on how they complement each other. Also, the theme of destiny and fate is common. Are they meant to be together? Writers often play with this idea, creating scenarios where they have to overcome obstacles to fulfill what seems like a pre - ordained relationship. And of course, the theme of adventure, as they might go on quests or face challenges together in the fanfics.
I'm not sure specifically which 'Kagome and Kouga Mate' fanfics are out there. You could try searching on popular fanfic platforms like Fanfiction.net or Archive of Our Own. Just type in 'Kagome and Kouga Mate' in their search bars and see what comes up.
One common theme is love triangle. Since Kagome has a relationship with Inuyasha as well in the original series, many fanfictions explore how kouga fits into this complex situation. Another theme is adventure. They might go on quests together in the fanfiction, just like in the Inuyasha story.
In many such fanfictions, a common theme is the cultural clash or融合 (since they come from different backgrounds in the original story). This can lead to interesting character development and relationship dynamics. There may also be themes related to protecting each other and the world around them, as their relationship might be seen as a source of power to face external threats.
Love against all odds is also a frequent theme. Given their initial enmity or indifference towards each other, seeing them fall in love and become mates is a central aspect. Their relationship often has to overcome obstacles like other suitors, family expectations (in sesshomaru's case, perhaps his clan's view), and their own personal biases.
One common theme is the overcoming of differences. Sesshomaru is a demon and Kagome is a human, so there's often a story about how they bridge that gap. Another theme can be the protection aspect, with Sesshomaru protecting Kagome from various threats.
Often, love and loyalty are common themes. The story might revolve around how they fall in love despite their differences. Also, the theme of sacrifice can be present. For example, one of them might have to sacrifice something from their own world or way of life to be with the other. There can also be themes related to family acceptance, as their relationship may face challenges from their respective families or groups.
Adventure is another one. Since they are characters known for their adventures in the original series, fanfics often continue this trend. They might go on new quests, fight new demons, and discover new magical items or places.
One common theme is the struggle between different eras. Since Kagome is from modern times and Inu no Taisho from the feudal era, there's often a clash of values and ways of life. Another theme is the power of love to bridge these differences. Their relationship is usually shown as something that can overcome all these obstacles.
One common theme is loyalty. Since they are mates, they are extremely loyal to each other in these fanfics. They will fight any enemy or overcome any obstacle to stay by each other's side.
The theme of redemption can be found in many 'sesshomaru x kagome mate fanfiction'. Sesshomaru may have a dark past or actions that he needs to atone for, and Kagome's love and influence help him on that path. Another theme is the exploration of new powers. Their union may unlock new abilities for either or both of them. And of course, the theme of acceptance, as they have to accept each other completely, flaws and all, in order to have a successful relationship.