Power - up is a common theme. Writers often explore how the white dragon gains new abilities and becomes stronger in the Highschool DxD setting.
Romance can also be a significant theme. The white dragon may get involved in romantic relationships with other characters in the Highschool DxD universe. This adds an extra layer of depth to the story as it navigates both the action - packed battles and the emotional aspects of love.
Power growth is a common theme. Fans often like to explore how the White Dragon Emperor can become even more powerful and overcome new challenges.
Power. Since it involves dragon gods, a common theme is the acquisition and control of great power. Characters often struggle with newfound dragon god - like abilities.
A common theme is power. The dragon slayer often has to deal with gaining and controlling their power in the Highschool DxD universe. Another theme is friendship, as they interact with the characters from the original series.
One common theme is power. Since both Dragon Ball and Highschool DxD have characters with different levels of power, fanfictions often explore how these powers interact. Another theme is friendship. Characters from both series form new friendships or rivalries in the crossovers.
Another theme is identity. The OC has to figure out how being a Dragon Emperor fits into their new life in the Highschool DxD world. They might struggle with whether to embrace it fully or keep it a secret. For instance, they may worry about how their friends and foes will react to their true identity.
Power - up is a common theme. Since Issei becomes a Dragon God, the fanfictions often explore his new powers and how he uses them to overcome challenges. Another theme is relationships. His relationships with other characters, like Rias and his friends, might change due to his new status.
One popular 'Highschool DxD White Dragon' fanfiction might be those that focus on the unique powers of the White Dragon and how they are developed further in new and exciting storylines. For example, some fanfictions could explore the White Dragon's interactions with other characters in different settings within the Highschool DxD universe.
One common theme could be the relationships between the characters. Since it involves Gabriel, there might be themes of friendship or rivalry with other characters from the 'Highschool DxD' universe.
Love and loyalty also pop up a lot. Highschool DxD has a lot of elements related to love and loyalty within its harem - like setting. When combined with Code Geass, fanfics may show how characters develop new relationships or test their existing loyalties. For instance, a character from Code Geass might find themselves in a situation where they have to choose between their loyalty to their original cause and the new relationships they form in the world of Highschool DxD.
Well, a fanfiction like this often delves into the lore of the White Dragon Emperor more deeply. Maybe it gives a backstory to some of his powers that the original series didn't fully explore. The OC in it could be a catalyst for change in the 'Highschool DxD' world. It could be a character from a different faction who comes to understand the White Dragon Emperor in a new way and helps him grow or face new threats.