OVA
Description
Professor Koyanagi is Tadashi's uncle, a scientist and inventor drawn into an outbreak of mechanized sea creatures. His father died of a heart attack in a hot summer factory; this same man developed the original mechanical leg technology later found on the infected creatures. That technology stemmed from Imperial Japanese Army WWII research aimed at creating a biological weapon using a virus that generated a deadly "death stench" odor.
While examining an infected fish in his lab, the creature's mechanical legs clamp onto Koyanagi's arm. He amputates his own arm to halt the infection's spread. Despite this trauma, he remains disturbingly fascinated by the machinery, prioritizing scientific curiosity over his well-being. Later, he constructs a custom walking machine and attaches the infected Kaori to it. During this procedure, he suffers a mortal wound when stabbed by the spider-like leg of Kaori's walker.
Mortally wounded, Koyanagi retreats to "Lab #2," the factory where his father died. There, he connects himself to a modified, advanced version of the mechanical legs. This new apparatus includes a zeppelin-like air balloon and a housing unit underneath capable of carrying a second person. In this transformed state, he attempts to kill Tadashi and Ms. Yoshiyama, potentially driven by jealousy or madness upon assuming their romantic involvement. After the attack fails, he captures Ms. Yoshiyama and flies away with her.
In the OVA adaptation, Koyanagi becomes antagonistic, attaching an infected Tadashi to a custom walking machine instead of Kaori. This version depicts his descent into madness through experimentation, culminating in his death when Tadashi's walker turns against him.
Koyanagi's final manga appearance shows the Citrous Circus pursuing his flying machine, attempting to bring it down with gas cannons. They puncture the balloon, but his machine deploys metallic wings, allowing his escape with the captive Ms. Yoshiyama. His anime adaptation role is significantly reduced compared to the manga, featuring limited screen time and a more straightforward antagonistic function.
While examining an infected fish in his lab, the creature's mechanical legs clamp onto Koyanagi's arm. He amputates his own arm to halt the infection's spread. Despite this trauma, he remains disturbingly fascinated by the machinery, prioritizing scientific curiosity over his well-being. Later, he constructs a custom walking machine and attaches the infected Kaori to it. During this procedure, he suffers a mortal wound when stabbed by the spider-like leg of Kaori's walker.
Mortally wounded, Koyanagi retreats to "Lab #2," the factory where his father died. There, he connects himself to a modified, advanced version of the mechanical legs. This new apparatus includes a zeppelin-like air balloon and a housing unit underneath capable of carrying a second person. In this transformed state, he attempts to kill Tadashi and Ms. Yoshiyama, potentially driven by jealousy or madness upon assuming their romantic involvement. After the attack fails, he captures Ms. Yoshiyama and flies away with her.
In the OVA adaptation, Koyanagi becomes antagonistic, attaching an infected Tadashi to a custom walking machine instead of Kaori. This version depicts his descent into madness through experimentation, culminating in his death when Tadashi's walker turns against him.
Koyanagi's final manga appearance shows the Citrous Circus pursuing his flying machine, attempting to bring it down with gas cannons. They puncture the balloon, but his machine deploys metallic wings, allowing his escape with the captive Ms. Yoshiyama. His anime adaptation role is significantly reduced compared to the manga, featuring limited screen time and a more straightforward antagonistic function.