In the city state of Lisvalletta, the citizens live peaceful lives by day while crime and illegal drugs permeate the area at night. A highly lethal drug “Anthem” has taken hold and the SEVEN-O Special Crime Investigation Unit is tasked with stopping it. Members of the unit operate in groups of two called the “Double Decker System.” Doug Billingham is a seasoned investigator, and joining him is Kirill Vrubel, whose abilities are mysterious and unknown.