User blog comment:Collbrande-Ex-Caliburn/Hyoudou Issei's Peerage composition hopes/dreams/hypothesis/@comment-26821288-20161228004608/@comment-9595671-20161229060954

True, but DxD also hasn't shown any other Gods of Death or a physical manifestation of it either. The fact he's the only God of Death is probably why he's only under heavy survellience as punishment for his actions in Volume 12 & 18, he doesn't have anyone to replace him.