The story is set in a world where humanity is ruled by the legendary "Seven Kingdoms." The main character Kasius is a "Kirin Rider," a warrior that purifies "Terrors" - beasts that threaten humanity. As a result of a battle against the Terrors, he encounters Shulip, a young witch who says that she is the 14th "Pure Maiden" sent from the "Pure Land." She is aided by the butler Barnette, and lives with Kasius and his sister Cleo at the house that they call "Lapis Lazuli" in the capital city of Baltra. On the "Breaker," an extremely high wall protecting the city, a masked man who calls himself "the Lord of Baltra" proposes a toast. This man, who controls the world from the shadows, welcomes Kasius and the others to the Seven Kingdoms.