As RoboRider, he fatally wounds Deathgaron before learning that the Hitomi killed was a fake and the real one was being taken to the Miraculous Valley. On his way, he meets Joe the Haze who is under the control of Nexticker, freeing him before they and Shigeru are captured by Maribaron and the Princess Karuoriya. It was after they break free that Kotaro realizes the princess is Hitomi, who was abducted to replace the real princess and was force grown by the nearby waterfall. When he attempts to restore Hitomi memory, Kotaro is forced to surrender when the Triplon captured Shigeru and Joe. Kotaro was then placed into a room for a hole designed to counter his abilities as both RX and RoboRider for a slow painful death. His rage to save those he loves invokes another new form, Bio Rider. After killing Triplon, with Shigeru's help, Kotaros in having Hitomi regain his memory as she and the others are return to their original ages by the people who originally resided in the valley. With only Joe and Shigeru knowing his identity, Kotaro returns to Earth. During the middle of the series, Shadow Moon mysteriously returns to seek revenge against him, shortly after, Shadowmoon was finally defeated when RX threw the Revolcane through Shadow Moon's Kingstone, effectively turning him good shortly before he died and finally reverting to Nobuhiko. In the finale, he was helped by the 10 veteran Kamen Riders to destroy the Crisis Empire.
Name: Kotaro Minami
Designation: Kamen Rider Black RX, RoboRider, BioRider
Weapons: King Stone
Rider Machines: Battle Hopper, Road Sector
After defeating Gorgom, Kotaro Minami found himself homeless until the Sahara family embraced him into their family. He found employment as a helicopter pilot for their family business, and began to build a new life for himself. But five years later, Kotaro was abducted into the interstellar mothership of the Crisis Empire. Knowledgeable of his identity as Kamen Rider Black, the organization attempted to offer him to join them. Kotaro refused so they threw him into space after leaving him incapacitated and split his Kingstone in half. However, the sun's radiation altered his Kingstone as he miraculously survived entry into Earth's atmosphere. Upon his rebirth, Kotaro learned he had evolved into Kamen Rider Black RX. With his new powers and vehicles, he battled the Crisis Empire and thwarted their plans to take over Earth. When Hitomi is kidnapped by Maribaron to assume the identity of the Crisis Empire's only living heir, Kotaro uses Deathgaron to enter the Desert of Death after them. By the time he finds Hitomi, Kotaro falls into a trap set up by Maribaron to do away with him and Deathgaron. When it looked as if Death Gron had actually killed Hitomi, RX was in a state of sorrow and sadness over the death of Hitomi invokes a new power, RoboRider.