Dark Kingdom
The Dark Kingdom is first referenced in Naoko Takeuchi's "", which features Sailor Venus as the main character, who confronts a group of villains called the Dark Agency. In the final volume of "Codename: Sailor V", the Dark Agency is revealed to be a subset of the Dark Kingdom, which leads to the beginning of "Sailor Moon". Takeuchi developed the "Sailor Moon" series and the Dark Kingdom when "Codename: Sailor V" was first proposed for an anime adaptation. The idea was ultimately dropped, but Sailor Venus became part of a new group alongside Sailors Moon, Mercury, Mars, and Jupiter, and instead of fighting the Dark Agency, they fought the Dark Kingdom.