A mysterious project, aimed at the destruction of Patlabor, progresses at the shores of Tokyo Bay. Detective Kusumi and Shinichiro go through a lot of trouble to investigate about the incident at Jounan. During that time, Shinichiro meets a university lecturer, Saeko. During their investigation, Kusumi and Shinichiro encounters "Monsters" at the reserves base who devours humans one after the other. Could these "Monsters" have anything to do with the assaults?
It was confirmed that some "Monster" scales were left behind but the situation has changed. The police and defense force were dragged in and before long, before Shinichiro knew what was going on, Saeko turns up. A shocking truth was being revealed. A self-defense force was manouevering things in the shadow.
As everything was getting more complicated, the "Monster" once again, lands on the shore of Tokyo Bay. For the sake of ending this sad war, Inguramu is started up.