One common theme is the exploration of their relationship. This could involve them falling in love, dealing with misunderstandings in their relationship, or growing closer over time. Another theme is adventure. Since they are often in some sort of action - oriented world, fanfiction might focus on their joint adventures, fighting against enemies and overcoming obstacles together.
The theme of sacrifice also pops up. In many stories, either Kai or Rei might be put in a situation where they have to sacrifice something for the other. It could be their own safety, a chance at power, or something else. And a third common theme is the discovery of self - worth. Through their relationship with each other, they might come to realize their own value, especially in a world that often challenges them.
One common theme is friendship. Rei and Usagi have a strong friendship in the original series, and fanfictions often expand on that. They might go through challenges together and come out stronger.
One common theme is the development of their relationship. It could be about how they first meet and start to have feelings for each other. Another theme might be adventure. They could be on a journey together and their relationship deepens during the adventure.
Love, either platonic or romantic, is also a frequent theme. Sometimes it's a slow - burn type of love where they don't realize their feelings for a long time. Other times it's a more immediate connection that they have to navigate through various obstacles in the story.
One common theme is friendship. Their bond might be explored as they face various challenges together.
Another theme could be self - discovery. Through their relationship, both rei and kazuki might learn more about themselves. In these fanfictions, they might have internal struggles that are resolved with the help of their friendship.
A theme that frequently appears is the power of their connection. Their combined powers or just their emotional connection can be a big part of the story. Also, there's the theme of acceptance. They accept each other's flaws and grow together. In some fanfictions, they face challenges that test their relationship, but in the end, acceptance prevails.
The mystery aspect. If 'kai' and'rei' are characters with hidden backstories or secrets, a horror fanfiction can explore those in a really dark and spooky way.
Survival scenarios are also quite common if these characters are from a post - apocalyptic or action - oriented anime. They might have to rely on each other in dangerous situations, which can bring out different aspects of their relationships. For example, Takashi might have to protect Rei and Saeko from threats, and this can strengthen or test their bond.
One common theme is survival. Given the setting of Highschool of the Dead, they often face challenges together and rely on each other for survival.
One common theme is the clash of cultures. Naruto comes from a world of ninjas and Rei might be from a different, perhaps more modern or post - apocalyptic setting. Another theme could be the power dynamic, as Naruto has his own set of powers and Rei may have hers. Their relationship development is also a common theme.