Kikaider00 (Pronounced Kikaider Double-O) is a novel by Masato Hayase and published in the Hobby Japan magazine from January 1999 to 2002. Coinciding with the releases were special figures and dioramas by S.I.C. preceding the S.I.C. Hero Saga. It tells an original story that serves as a sequel to the TV series and introduces a previously manga exlusive character, the title protagonist Rei (Kikaider 00). Characters from other Ishimori Productions series such as Kamen Rider 1, Robot Detective K and Kamen Rider V3 have appeared in some chapters.
Several years after the defeat of both DARK and SHADOW, Jiro had spent time looking for his brother Ichiro and their comrade Bijinder who had both disappeared. During a rainy night, lightning struck a church Dr. Komyoji was staying at. Outside, he encountered an android with an appearance similar to Kikaider, Kikaider 00 (Rei). In Jiro's absence, a new organization called XASH had surfaced and Rei must fight against them.