Half a year after the battle with Golugom, the peace that was supposed to be restored was suddenly broken by the demon world, the Clexis Empire. General Jack of the Clexis Empire wanted to recruit Minami Kotaro as a subordinate, but Kotaro refused, so General Jack destroyed his transformation function. With the transformation function destroyed, Kotaro was thrown into space. When Kotaro was about to turn into space dust, he was exposed to the mysterious sunlight, and the Emperor Stone in his body also changed. As a result, Kotaro became the new prince of light, "Son of the Sun" Kamen Rider BLACKRX, and started a battle with the Clexis Empire.