A series of natural disasters has reduced the world to rubble, with the survivors doing whatever they must to survive in a world gone mad. But one young boy, Kakugo, gifted with amazing martial arts and a superpowerful suit of armor by his late father, has been charged with making the world (or at least his school) a safer place. But his sister has a matching set of skills and equipment, and she`s on a mission to bring peace to the world... by wiping out humanity!

Life could be better for shy, anxious university student Rin. The apartment she has rented is hardly the sunny palace the rental listings suggested. The housing complex is rundown, grim and haunted by troubled souls lurking in dark corners. Ghastly crimes are occurring in the vicinity. And a grinning stranger makes his unsettling presence known. Beyond all this, Rin is coming to realize that something even more sinister is manifesting itself, something at the cursed crossroads of mythology, monstrosity and medical science. Determined to find out more, Rin visits the library, where she meets a sympathetic young staffer. But what she learns does not begin to put her mind at ease.

The story follows Elk, a bounty hunter in some strange futuristic world. On this world archaic but advanced technology exists side by side with primitive attitudes, beasts and magic. In other words it's got a bit of everything. It also has an evil conspiracy who are able to produce powerful monsters called chimera, who can also appear as human. Naturally it is not long before Elk has rescued a young female beast-master and gained himself some serious enemies.

Hyoudo Riki is just an ordinary guy who likes to wear a tiger mask while Kung-Fu fighting, which means he fits in real well at BATTLE ROYAL HIGH SCHOOL! Unfortunately for Riki, he`s the doppleganger in our world of Byoudo, Master of the Dark Realm, and when a dimensional gate opens between the two worlds, the evil Fairy Master tricks Byoudo into making an attempt to conquer our beautiful, and better lit, world. Now poor Riki is semi-possessed by his opposite number, and the minions of the Fairy Master are mutating his classmates into hideous lustful monsters. To make matters worse, all the inter-dimensional commotion has attracted the attention of a sword-happy exorcist and the heroic Zankan of the Space-Time Police! Which all means that Riki is about to take one bitch of a mid-term. The course is survival, and forget "Pass/Fail". The test is graded "Live/Die".