User blog comment:Ariel Saeba/Mythology and Character Origins in DxD/@comment-28087290-20160413071356/@comment-28087290-20160510235025

@Swampy Thanks and hey, Issei's daughters with these two in EX reference Yin and Yang because one can't exist without the other and the daughters were born on the same day, so kind of implying if they hadn't been born together on the same day, one of them would have died. Because it would of caused unbalance to the relationship of their mothers who represent Yin and Yang.