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English translation of the Japanese manga 666 Satan.
It has been heavily marketed as the series made by the Naruto author's twin brother.
In the not too distant future, mankind fights over relics from an ancient civilization called O-Parts, each of which contain incredible powers. Some people with special abilities are able to use the O-Parts to their full potential, and are known as O.P.T.s (or O-Parts Tacticians). Naturally, O-Parts can be used for both good and 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.s, and inside him sleeps a demon of incredible ferocity. He meets up with a girl named Ruby who, like her famous father before her, wants to become a treasure hunter. Though Jio doesn't believe in friendship, he agrees to be Ruby's bodyguard, and together they go on a dangerous quest to discover as many O-Parts as they can.