Ruby's dream: to become a famous treasure hunter. Jio's dream: to rule the world!
In a not too distant future, mankind battles over O-Parts, powerful relics from an ancient civilization. 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 also a very powerful O-Parts Tactician (O.P.T.), and inside him sleeps a demon of incredible ferocity. With his partner, Ruby, Jio embarks on a dangerous quest to acquire as many O-Parts as he can.
A chance encounter and a case of mistaken identity pit Jio and Cross against each other in a battle that almost seems foreordained--and though Cross is unaware of the creature lurking inside Jio's heart, he can't fight the strange feeling that they've met somewhere before. Will Ruby be able to intervene before these two formidable O.P.T.s tear each other apart?