In the present time, Earth is under invasion by the Kingdom of Great Lunarium based on the moon. It is a matriarchal society ruled by a queen, and authority is held primarily by women. Members of society are divided into several rigid castes. These are, in descending order: the queen class Double Moon, the princess class Full Moon, upper-class Half-Moon, lower-class Crescent Moon, and the soldier-class Piece-Moon. Every person is born with a crest on their body, and this crest determines his/her caste.
Katsuma is a Crescent Moon. In the Queen’s immediate circle, the executives, Katsuma is the lone male. The others treat Katsuma as a gofer due to his caste and poor martial prowess. When ordered into battle, he is consistently defeated. Furthermore, whenever the female executives make a mistake, they would also blame it on him.
Things change one day. The Full Moon Lunatemis suffered a major defeat in an expedition to Earth, and Katsuma is directed to administer her punishment. Now, he can finally put his secret plan into motion, for Katsuma possesses Emblem Steal, an ability to steal another person’s crest!