The lore I had:
Demon species are ranked on hierarchy.
SSS Rank, those OP demon species that are hax for example a Kitsune and other demons that are considered "Godly".
SS Rank, whatever it may be and Dragons are possibly in this rank.
S Rank, the likes of Vampires and Werewolves belong here.
^This ranking is based on species.

Having belong to an S Rank specie is a feat and of course this rank is based on Nobility and Royalty.
Creatures of the night like Vampires and Werewolves etc are only at their strongest at night.
Vampires and Werewolves at day time are at 30% or less of their strength.