Shiro Kanzaki is a central character and the main antagonist in the series Kamen Rider Ryuki. As the architect behind the Rider War, he manipulates the events from behind the scenes, using his alter ego Kamen Rider Odin. Driven by a desperate desire to save his sister Yui, Shiro orchestrates the deadly battles among the Riders, offering them a wish in exchange for victory. His actions and motivations drive much of the conflict and intrigue throughout the series.