Friend of Foe? The Mysterious Riderman

Ambitious Destron scientist Yuki Joji is condemned to death by Marshal Armor, who sees him as a threat to his position in the organization. Slowly Yuki is lowered into a pool of sulfuric acid, losing his right arm before being rescued by his fellow scientists, who make a daring escape. Hidden away, Katagiri contacts his sister, who is a nurse, to assist in Yuki's cybernetic operation. But Destron is watching and sends Sickleneck-Tortoise to kill them…