Reiko

Reiko as encountered by Aya and her party from time to time is in fact no single-person but clones of a scientist that is working to unlock the secret behind the zombie outbreak since its beginning. The clones at first were created for the original Reiko to experiment on with the Baneful Blood and presumably meant to be expendable. This has apparently changed later when, in order to more-efficiently carry out her will, the original Reiko wired herself into a computer network and began developing more-sophisticated clones to serve as her eyes and ears in the field. These new generation of clones, benefiting from progress made on Humanity's understanding of the Baneful Blood descendants (for example, excessive exposure to the Baneful Blood triggers "berserk" reaction on them instead of outright killing them), are divided into two categories: the "Single Digits" model, the nine clones based on the original Reiko, and the mass-production model, simplified versions of the "Single Digits" model. All clones have been genetically enhanced for their specific functions, but only the "Single Digits" model is capable of the full-range of investigative tasks from intelligence gathering to self-defense combat. Also, all nine Single Digits clones are telepathically linked to one another and the original Reiko.