Koneko Toujou is popular as well. Her small and cute appearance combined with her strong fighting abilities make her stand out. In fanfiction related to the Red Dragon Emperor, she might be depicted as having a sister - like relationship with him or even having her own character arc that intersects with his.
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.
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.
Rias Gremory is often paired with the Nightmare Dragon Emperor. Their relationship can be filled with tension, as they both have strong personalities and leadership roles within the story. Their interactions can range from strategic planning to more personal, emotional moments.
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.
Obviously, the Blue Dragon Emperor himself is extremely popular. He's the central figure in these fanfictions, and his journey of power - seeking and self - discovery is often the main focus.
Rias Gremory is also quite popular. Her relationship with Issei, whether it's romantic or just as comrades, is a big draw. Fans like to explore different aspects of their dynamic, like how she helps Issei control his powers or how they face challenges together.
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.
Asia Argento is another option. Her kind - hearted and innocent personality could be a contrast to the more battle - hardened Heavenly Dragon Emperor. Their relationship could develop in a way that shows how he protects her and she in turn helps him see the good in the world around him, adding an emotional depth to the fanfiction.
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.
Great Red is also a very popular dragon in Highschool DxD fanfiction. Given his mysterious and powerful nature, many fanfictions explore his potential influence on the main characters' lives and the overall plot of the story. His abilities are often expanded upon in these fan - created works.
Sasuke could also be a main character. His relationship with Naruto might change due to Naruto having the power of the Red Dragon Emperor. Maybe he would be jealous at first, but then they could end up working together to face new threats that this power has attracted. Sakura might also be involved, perhaps she tries to help Naruto control the new power or she is worried about the changes in Naruto.