666 Satan has been released internationally in Spain, France, Italy and North America, although, Viz Media changed the title to O-Parts Hunter in the latter.

O-Parts (オーパーツ, Ō Pātsu), named after out-of-place artifacts (OOPArts), are ancient relics found throughout the world, left by an extinct civilization from before mankind existed.

They are being searched for by the Stea Government (Angels) and the Zenom Syndicate (Demons) who want to insert them within the Kabbalah (正カバラ, Sei Kabara, lit.

A legend tells that when either Kabbalah is filled, a super weapon called the Legendary O-Part (伝説のオーパーツ, Densetsu no Ō Pātsu) will be awoken.

Set in the near future, it tells the story of a teenage girl named Ruby Crescent who wants to become a treasure hunter, following in the footsteps of her father.

The series' retains the original 666 Satan name in all the other countries it has been released, such as in France by Kurokawa,[14] in Italy by Edizioni BD's J-Pop division,[15] in Spain by Glénat,[16] and in Taiwan by Chingwin Publishing Group.

They finished their review by saying instead of relying on cliffhangers to get the reader to buy the next volume, "Kishimoto depends on another, more difficult-to-achieve effect—generating real concern for Jio and his friends, regardless of what comes next.

"[20] Jason Thompson declared Viz Media's changing of the series' title to "O-Parts Hunter" in North America one of "The Greatest Censorship Fails" in manga.