Another theme is character relationships. Writers often explore how the characters from the two series interact with each other. This could be in terms of friendship, rivalry or even romance. For instance, Ichigo from Bleach might form an unexpected friendship with Issei from Highschool DxD.
The exploration of different universes is also a big theme. Fanfiction writers like to play with the idea of how the two very different universes of Bleach and Highschool DxD co - exist and affect each other. They might create stories where the characters have to travel between the two universes to solve a common problem.
One common theme is crossover battles. Writers often like to imagine how the characters from Bleach would fare against those from Highschool DxD in combat. For example, Ichigo might be pitted against Issei.
One common theme is power - up. Just like in a game, the characters often level up or gain new abilities in these fanfictions. Another theme is strategy. They use gamer - like thinking to plan their moves against opponents in the Highschool DxD world.
One common theme is the exploration of their relationship in a supernatural setting. Since Highschool DxD is full of demons, angels, and other mythical beings, their relationship might be affected by these elements. For example, they might have to fight together against a common enemy, which would strengthen their bond.
One common theme is the struggle for acceptance. The disabled oc often has to face the challenges of being different in a world full of supernatural beings. Another theme could be self - discovery, as the character figures out their place in the Highschool DxD universe.
One common theme is friendship. Their relationship is often depicted as a strong bond that helps them through various difficulties in the Highschool DxD universe.
One common theme is power. Since Tiamat is a very powerful being in the 'Highschool DxD' world, fanfictions often explore how Issei's power grows or is affected by his relationship with her.
Friendship is a common theme. Tsubaki and Sona often start with a pre - existing friendship in the fanfictions and it either deepens or is tested. For example, they might have to support each other through tough times at school or in the supernatural world.
One common theme is the clash of different worlds. Death the Kid comes from a very different universe compared to Highschool DxD, so there's often a lot about how they adjust to each other's rules and cultures.
Well, a big theme is self - discovery. The male reader in these fanfictions often has to figure out who he is in this new and crazy world of Highschool DxD. There's also the theme of loyalty. He has to decide which side he's on, whether it's the devils, angels, or something else, and be loyal to that cause. And let's not forget the theme of friendship. He forms bonds with characters from the original series, and these relationships play a big role in the story, whether it's helping him in battles or just being there for him in tough times.
Power - up themes are also common. Naruto already has his powerful ninja abilities, and when combined with the magic and power systems in High School DxD, there are often scenarios where he or Sona gain new powers or find new ways to use their existing ones. For example, Naruto might learn to combine his chakra with Sona's magic for a super - attack. Another theme is friendship and alliance. Since they are from different worlds, they need to form an alliance to face common enemies. This often leads to the development of a deep friendship between them as they rely on each other's strengths.