Tsuyoshi Shirakawa features solely in the OVA adaptation as a freelance videographer who first meets Kaori aboard a flight bound for Tokyo. His core objective revolves around securing research data from Dr. Koyanagi, prompting him to shadow Kaori to the scientist's facility. Shirakawa records the intensifying catastrophe of mechanized aquatic creatures and infected humans throughout the unfolding events. Prior to these incidents, both his parents committed suicide under undisclosed circumstances. By the OVA's conclusion, Shirakawa becomes infected by the walking fish pathogen. Before the infection consumes him completely, he aids Kaori in joining a survivor group.