Four hundred years ago, a meteorite gave birth to monsters that could only survive by consuming human flesh and blood. These monsters, adept at hiding among people and stalking their prey, were known as the Aliens. In response, the Federation established the Federal Alien Countermeasures Bureau, also known as "FACA," using the genetic cells of the Aliens to cultivate elite officers to combat them. An Ran was one of the most outstanding officers, but he harbored a secret, possessing another identity: "she," a member of the Alien race…