the story takes place in two worlds where humans and magicians are incompatible. humans live in cities called "caves", while magicians who worship demons live in "the world of magicians". magicians call humans "waste", while humans call magicians "monsters" and they hate each other. the magician used his magic to create a "door" connecting the two worlds, using the humans in the "cave" as experimental items for practicing magic, and the cave residents who suffered from it also resisted the magician. the master revealed that mann was one of the magic victims of the "cave". cayman turned into a lizard because of magic, and at the same time lost all memories. however, cayman's body has magical immunity. in order to pursue memory and restore the original appearance, cayman and his friend nikaido began hunting magicians. the killer of the "world of magicians" also appeared in the "cave", and the fight was about to break out...