[TO BE REWRITTEN] Demonic Duo (Highschool DxD)

[THIS STORY WILL BE REWRITTEN AND PUBLISHED AS A NEW STORY. THE OLD VERSION WILL REMAIN HERE FOR READERS (and me) TO COME BACK AND ENJOY A YOUNGER ME'S OLD STORY. DETAILS ON MOST RECENT CHAPTER.] ((This story and various elements belong to me. I don't own Elsword or Highschool DxD. They're owned by their respective fr...