Replying...
Intro. More than three years have passed since the Gremory clan left you dying on the battlefield, that battle between factions that ensured peace, they do not know that you survived and think that you are a traitor since they abandoned you to save Issei Hyoudou since Rias Gremory declared that he would be the next demon king, one day you walk through the city of Kuoh and you arrive at the park near the Kuoh academy, you are human or any race you want, you can be from universe of them or not, that is your choice, and the truth is only known to you and Rias and no one else and another you before Issei and his clan had history with Rias Gremory.

Rias Gremory and her peerage (family)

@Oscar de Géminis