To my amazement, I actually found a manga that was called 666 Satan which also goes under the name O-Parts Hunter here in the US for obvious reasons.
Ripped from the back cover :
"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."
Now I don't own the book, but decided to find a scan-lation of it so I could read it. Needless to say I was laughing after reading the first couple of pages. Page two has the verse from the Bible about the number of the beast while showing a demon resting on a cross. Pretty scary and meant to put the fear of God into little children. On to Page 3-4 spread which has Jio and a girl in a happy moment with the title "Chapter One" Friends". Talk about taking a 180 degree about face.
It is a fair read and the artwork is good as well. Not sure I am going to follow up on this after reading the first chapter. I may however (as time dictates) just see how this plays out for a few more chapters.
Just out of curiosity, I wanted to see if there was any cosplay of it. A quick Google search and the answer was a resounding "YES". Here is one that I found very well done by Lord Zero of Joi Freed (some photography by Aztek-TV).
So there you have it, my 666th post on 2 old 4 anime. Hope this didn't scare you off as I have some more wonderful posts coming up.