Six years ago, Tsukihiko was caught in an assassination attempt on a little girl, Sami, when he attempted to be her shield. This incident nearly killed him and the girl together, but the little girl was the daughter of an extremely powerful family. With its vast amount of resources, the family was able to keep both Tsukihiko and Sami alive by recreating both of their bodies with cyborg technology. This has forced Sami to permanently rely on wired connection to her life sustaining computer. On the other hand, Tsukihiko has become a cyborg "Knight," sworn to protect Sami from harms way. (Source: MangaHelpers)

Another world exists one level below the one we live in, the Rengoku. Rengoku is filled with a poisonous gas called "ren". Although "ren" is harmful to the human body, it brought many new possibilities to mankind. Artemisia also known as Alto is the first princess of the country Ei. She has an abnormal body which is a doorway connected to the Rengoku. Because of this her body emits "ren" uncontrollably, bringing death to the people around her. As a cursed princess, she is locked up in the castle's dungeon, living her life without daylight. One day Alto met a young knight named Fog and together they received an order from the royalty. Alto's goal is to become a "Rengokushi", controlling the exceptional power that "ren" brings. "Come, let us dance in the sorrowful Rengoku!"