Kamen Rider Black
During the events of "Black RX", Kohtaro lives with the Sahara Family and is captured by the Crisis Empire who ask him to join their side. When Kohtaro refuses, they shatter his King Stone into two pieces, thus rendering him unable to transform into Kamen Rider Black. They throw him into outer space, where the sun's radiation mutated his King Stone, allowing him to evolve into Kamen Rider Black RX to fight the Crisis Empire and the Strange Demon Soldiers.