Kamen Rider Black.

Minami Kotaro and Nobuhiko Akizuki grew up together, as close as brothers, having been born at the exact same time and their fathers having been best friends. Together with their sisters Katsumi and Kyoko they experienced an idyllic youth and wanted for nothing. All that changed though on their 19th birthday, wherein they discovered their fathers were members of the sinister Golgom cult and that their births took place at just the right moment during a solar eclipse to mark them as Century Kings, candidates to become the new Creation King for Golgom and conquer the world. Minami Kotaro manages to escape before he can be brainwashed and thus is able to use the powers forced upon him as Black Sun to fight as Kamen Rider Black! But can he rescue Nobuhiko before he is transformed mind, body, and soul into Shadow Moon?

( There is a lot to be covered in this series. )