The Mikazuki Syndrome, a pollution-related disease, causes various symptoms among the residents who eat fish caught in the Mikazuki Bay. The cause is the wastewater discharged from plants attracted along the mid stream of the river into the sea. The government then sets up Relief Committee for the Mikazuki Syndrome. Fox, one of the doctors in the committee, asks Black Jack to participate in as a special contributor. Black Jack and Pinoko, staying in the suburbs of Crescent City, meet a girl named Tsukiko who lives on her own by selling fish caught in the Mikazuki Bay.