One common theme is the development of relationships between the main characters. For example, the relationship between Issei and the various female characters often has a lot of twists and turns. Another theme could be the exploration of the supernatural world within the context of the relationships. Like how the different devil clans and their powers interact with the romantic storylines.
Well, often there's the theme of self - discovery within the romantic relationships. The characters, especially Issei, grow as they fall in love and face different challenges in their relationships. Also, loyalty is a big theme. Whether it's loyalty to a partner or to one's group while being in a romantic relationship. For instance, when Issei has to choose between helping his friends and spending time with his love interest.
In these fanfictions, the power dynamics within relationships can be a significant theme. Given that in the 'High School DxD' universe, power levels are important. So, when characters are in a romantic relationship, how they balance their own power, their partner's power, and how that affects their relationship is often explored. For example, a more powerful character may have to be careful not to overshadow their partner, or they may use their power to protect their loved one in different ways.
Issei is definitely one of the most popular characters. Since he's the main character in the original 'High School DxD', he often takes center stage in the fanfictions too. His relationships with Rias, Akeno, and other female characters are frequently explored in a romantic context.
Power growth is a very common theme. Writers often explore how the characters can become stronger in different ways compared to the original story. Another common theme is relationship development, like the romantic relationships between characters.
Many fanfictions focus on Issei's role within the devil society. How he rises in rank, earns respect, and changes the way things are done. There are also themes related to loyalty and friendship. His relationships with his friends and comrades are often explored, showing how they support each other in the face of various challenges in the dangerous world of 'High School DxD'.
A common theme is the clash of technology and magic. The terminator's mechanical and technological nature often stands in contrast to the magic - based world of DxD.
One common theme is power - up. Characters from both Naruto and DxD often gain new powers or abilities when combined in fanfiction. Another theme is the exploration of different cultures. Since Naruto has its ninja culture and DxD has its own demon and angel - related cultures, fanfictions often explore how these cultures interact.
One common theme is power - leveling. Just like in regular gamer stories, the characters in dxd gamer fanfiction often strive to increase their stats and abilities through various in - game - like mechanics. For example, they might defeat powerful enemies to gain experience points.
One common theme is power. Godzilla is extremely powerful, and in the DxD universe which also has powerful characters, exploring how his power compares and interacts is a big theme.
Another theme is the exploration of the afterlife. Given that reapers are associated with death and the afterlife, fanfictions often explore how the DxD world's view of life and death is affected by the presence of a reaper. They might show how the reaper's knowledge of the afterlife changes the perspective of the DxD characters.
A common theme is the clash of different power systems. Since Odin comes from Norse mythology and DxD has its own complex power structure, seeing how they interact is often explored. Another theme is the idea of prophecy. How Odin's knowledge of the future might play a role in the DxD world's events.
Another theme is the clash of cultures. Naruto comes from a ninja - based culture, and DxD has a very different supernatural culture. Fanfictions often explore how Naruto reacts to the different social norms, values, and power structures in DxD. It can be really interesting to see how he tries to find his place in this new world.