One popular storyline could be the OC's struggle to control the power of the Red Dragon Emperor. For example, they might face challenges in taming the intense and sometimes uncontrollable power within them. Another could be their relationships with the existing characters from Highschool DxD. They might form alliances or rivalries with Rias and her peerage. Also, a story could revolve around the OC uncovering secrets related to the Red Dragon Emperor heritage that were previously unknown, leading to new adventures and battles.
Well, some storylines involve the OC dragon having a special bond with one of the main characters from Highschool DxD. This bond could be based on a shared goal, like finding a powerful artifact that is important to both the dragon and the character. It could also be a more emotional bond, like the OC dragon helping a character through a difficult time. There are also storylines where the OC dragon is an outcast from their own dragon clan and has to prove themselves in the world of Highschool DxD.
One interesting storyline could be the Red Dragon Emperor exploring new powers. For example, he might discover a hidden aspect of his Boosted Gear that allows him to access a different form or ability. This could lead to him having to train in new ways and face challenges that he wasn't prepared for before.
The 'Redemption' trope is often seen in 'Highschool DxD White Dragon Emperor OC Fanfiction'. Maybe the OC has a dark past that they are trying to atone for, and their relationship with the White Dragon Emperor helps in that journey. The 'Alliance' trope is also popular, with the OC forming an alliance with the White Dragon Emperor against a common enemy. This can lead to epic battles and strategic planning within the fanfiction. And don't forget the 'Discovery' trope, where the OC discovers something new about the White Dragon Emperor or vice versa, which can change the course of the story.
First, give your OC a unique backstory related to the Red Dragon Emperor power. Maybe they didn't inherit it in the traditional way, or there was some sort of prophecy involved. Second, define their personality traits clearly. Are they more hot - headed like Issei in some ways, or are they calmer and more calculating? Third, think about their goals. It could be something as simple as becoming the strongest in the school or something more complex like uniting all the different supernatural races. And don't forget to give them some flaws, like being overly confident at times which can get them into trouble.
Akeno Himejima is also a favorite. Her dual - nature, being both sweet and having a darker, more sadistic side in battle, adds depth to her character. In fanfiction, she can have different interactions with the Red Dragon Emperor, from being a close ally to a potential love interest.
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.
One popular storyline could be Gabriel's interaction with the main characters from Highschool DxD in a more peaceful school setting. For example, she might be involved in a friendly competition among the different factions at the school. Another could be a story where Gabriel has to adapt to the modern human world while still maintaining her angelic duties. She could face challenges like understanding modern technology or human emotions.
One popular storyline could be a crossover where characters from 'King of the Holl' interact with those from 'Highschool DxD' in a battle for supremacy. Maybe the power dynamics between the different species in both universes are explored. Another could be a story where a character from one series tries to adapt to the rules and culture of the other series. For example, a character from 'King of the Holl' having to deal with the school life and devil politics in 'Highschool DxD'.
One idea could be a dragon OC that has the ability to transform into different elemental forms. For example, it can be a fire - breathing dragon in combat situations, but a water - based dragon for healing or stealth purposes. This would add an interesting dynamic to the story as it could befriend different characters based on its form.
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.