The near future not far from the present...
"M City" is an immigrant city with complete social welfare, public facilities and medical systems. Behind its government is "Otsuka Pharmaceutical", a private company that started out through smuggling and monopoly of necessities after the war. On the surface, "M City" is a livable holy place, but inside it is an unknown hotbed of crime.
The origin of the incident was a corporate accident involving "Otsuka Pharmaceutical" researching "lysogenic cells" half a year ago. In order to cope with the further strategic goals of the board of directors, "lysogenic cells", which were originally intended to be able to repair the body's decaying cells, came into being. Due to an accidental research accident, the water source at the chemical reagent discharge site was misused by a private water dispenser company, resulting in a small-scale infection. After the company discovered and blocked the spread, it has infected about 500 citizens, and the infected people without exception developed a strong urge to eat people (the infected people later called them "protozoans"). The company headquarters established a mobile squad "A. T. T. A. C. K" to carry out expulsions...
The activities of the "original body" became out of control. Several female college students disappeared one after another at the City University of Fine Arts. At the same time, the "A. T. T. A. C. K" investigation team discovered a large number of "protozoans" gathering reactions in a club hotel in the city. The battle between the mobile squad and the "original body" gradually showed signs of fatigue. At this time, the senior management of the headquarters proposed a preliminary proposal for a mysterious plan...