Kotaro Minami was born on the day of a solar eclipse alongside his step-brother Nobuhiko, revered by the Gorgom as the heirs to their leader's throne: the Century Kings "Black Sun" and "Shadow Moon". Once the two were of the ideal age, the Gorgom captured them and infused them each with a Kingstone. However, Soichiro Akizuki, the boys' father, interrupted the final mind-altering stage of the surgery and Kotaro barely escaped with his life while Nobuhiko was in a state of hibernation. After Soichichiro was killed for his actions, Kotaro took on the name of Kamen Rider BLACK to fight Gorgom and his friend-turned-enemy before destroying the Creation King.