Well, perhaps the concept of the character's growth is interesting. In the fanfiction, the son of Trihexa might start with a certain level of power but then have to face various challenges that force them to grow and develop new skills. Also, the idea of their place in the overall power structure of the 'Highschool DxD' world is fascinating. Are they a threat? Or could they be an ally? And how does their existence change the political and social dynamics among the different supernatural groups.
One interesting concept could be the unique powers that the son of Trihexa might possess. Given Trihexa's status in the 'Highschool DxD' universe, the offspring could have extraordinary demonic abilities that set them apart from other characters. Another concept might be how this character interacts with the existing factions like the Devils, Angels, and Fallen Angels. Their heritage could lead to both suspicion and attempts to befriend or control them.
Obviously, the son of Trihexa is one of the main characters. His actions and development would be central to the story. Then there could be characters from the original 'Highschool DxD' series like Issei, who might interact with this new character in various ways, either as an ally or an opponent. Rias could also be a main character as she is an important figure in the original series and her reaction to the son of Trihexa would be significant.
Yes, there might be. The Naruto and Highschool DxD universes are both quite popular, and the idea of combining them with a Trihexa element could be an interesting concept for fanfiction writers. You can try searching on popular fanfiction websites like Fanfiction.net or Archive of Our Own to see if such a story exists.
A plot could involve the main characters having to form an alliance with Trihexa to face an even greater threat. They would have to find a way to communicate and work with it, which would be a huge challenge considering its nature. This could lead to some interesting character development, especially for Issei as he tries to understand and tame Trihexa.
Perhaps in this fanfiction, Naruto's skills and abilities from his own universe are used to deal with the chaos that the Trihexa might bring in the Highschool DxD world. He could form alliances with the characters from Highschool DxD and together they try to either control or defeat the Trihexa. It could also explore how Naruto's ninja way clashes or meshes with the values of the Highschool DxD characters. This could lead to interesting character development and plot twists as they navigate through the challenges presented by the Trihexa.
Issei could still be the main protagonist. His determination and ability to grow stronger could play a big role in any story involving Trihexa. He might be the one to face Trihexa head - on or try to befriend it.
In Gilgamesh Highschool DxD fanfiction, there might be concepts like Gilgamesh forming alliances or rivalries with the devils, angels, and fallen angels in the Highschool DxD world. His vast treasures from his own story could also play a role, perhaps being used as bargaining chips or powerful weapons in the battles that often occur in the Highschool DxD setting.
One interesting concept could be the crossover of the Highschool DxD world with the eerie and mysterious Slender Man. For example, how the characters in Highschool DxD, with their unique powers and personalities, would react to the presence of the Slender Man. Maybe the devils in Highschool DxD would try to make a deal with the Slender Man or fight against him to protect their territory.
In Aizen Highschool DxD fanfiction, a cool concept might be how Aizen's Zanpakuto abilities would translate in the Highschool DxD setting. His Shikai and Bankai could have new and unexpected effects. Maybe his illusions could be used to deceive not just in battle, but also in the social and political intrigue that is so common in the Highschool DxD world among the different factions.
In some Highschool DxD SI Fanfiction, the self - insert might come from a different world or time period. This brings in elements of cultural shock and different knowledge systems. They could introduce new technologies or fighting styles to the world of Highschool DxD, which can lead to very creative and engaging storylines.
One interesting concept could be a crossover where the characters from Highschool DxD encounter Slenderman. Maybe the devils in Highschool DxD are intrigued by Slenderman's otherworldly and spooky nature. They might try to either recruit him or fight him, depending on their motives.