Bloodthirstiness… The desire to kill someone… These strange concepts—at least to some people—have always chased humankind. And even if you strip them of all technology, opportunities, and knowledge, they will still look for a way to kill and maim. At best, to injure. But they will never give up the chance to spill someone else’s blood. Because even knowing about the many bloody wars of the past never stops them. It’s as if the memory of such horrors simply erases… Whoever it is—powerful and extremely cruel—who conducts a terrible experiment over Mankind.