In a world where humanity has turned into prey against monstrous bug-like creatures dubbed "White Skins", one legendary figure known simply as "Ryuuma" continues to give hope to this post-apocalyptic society. This individual has many faces and descriptions, but his/her legend has lived continuously in the hearts and minds of the people for half a century, though no one knows where or how it started. Here starts a chronicle to unveil the mysteries of a legend.