After the downfall of Gorgom, Kohtaro Minami has gotten a job as a helicopter pilot in a business owned by the Sahara family, who have also taken him into their home. Kohtaro is later captured by the Crisis Empire and offered a place in their group. When Kohtaro refused, his King Stone was shattered and he was thrown into space where the sun's radiation mutated his King Stone and he mutated into Kamen Rider BLACK RX. With his new powers, he battles the Crisis Empire and thwarts their plans to take over Earth.