- I heard this in a few fanfics I dont know if it is fanon canon or a real fact of Japanese mythology but the Japanese Heaven is ruled by three Major Gods, each of whom take turns playing out the role of Kami-Sama according to a complex schedule of time and season. The first is the Sun Goddess, Amaterasu Omikami, the second is her brother, Tsukiyomi, the Moon God, and third is Susanowa, the Lord of Storms and God of the Seas. In the beginning of all things when Japan was young and freshly conquered from the Ainu these three divided up the world between them, each ruling their separate quarter as an independent fiefdom, subject to the will of the Celestial Overlord, who is enigmatic and mysterious beyond the ways of Gods and Mortals. Then around about the end of the ancient Feudal period, when Japan had been torn apart by generations of war, and the Gods had fought numerous battles against the tribes of the demons, it was decided that everyone and everything would come under the dominion of the triune powers, the Three who would each take turns holding the office of Kami-Sama.
We know that both Amaterasu and Susanowa are currently reincarnated that would make Tsukiyomi the current Kami-Sama when Hecate executed a plan. This can also lead to a little Fridge Brilliance. I always suspected that Susanowa was Belldandy, Urd and Skuld's father during the series they always called Kami-Sama father yet never during Divine Blood. So Tsukiyomi took the title recently. Which would explain why Peorth who I suspect is his daughter became Kami-Sama after his death.