In the not too distant future, mankind battles over O-Parts, relics from an ancient civilization. It takes a special kind of person to unlock the full potential of these remnants from the past, and a unique breed of humans known as O.P.T.s (or O-Parts Tacticians) become a force to be reckoned with. Unfortunately, O-Parts can be used for good or evil purposes. Jio is a young boy with a tragic past who only trusts one thing in the world: money. Little does he suspect that he is actually a very powerful O.P.T., and inside him sleeps a demon of incredible ferocity. He meets up with a girl named Ruby, and together they decide to embark on a dangerous quest to discover as many O-Parts as they can. Will Jio help Ruby realize her dream of becoming a world famous treasure hunter? More importantly, will Ruby help Jio realize his dream of--world domination?! (Source: Viz Media) Included one-shots: Volume 6: Trigger

666 Satan was published in English as O-Parts Hunter by VIZ Media from December 12, 2006 to December 8, 2009; in Italian by J-POP from June 6, 2008 to July 25, 2010; and in Spanish by EDT/Glénat from July 2009 to June 2012.