The O-Parts Hunter manga series, known as 666 Satan in Japan, features a cast of characters created by Seishi Kishimoto. 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. Her objective is to find O-Parts, ancient relics that can only be used by O.P.T.s (O-Part Tacticians), people who are able to release their Spirit and focus it into an O-Part to activate a special Effect, usually of a fantastic nature. She meets a mysterious boy named Jio Freed who, due to having a dark, lonely past, seeks to conquer the world. Jio is hostile to her at first but ends up traveling with Ruby as her bodyguard.
Throughout the world, there are ten Angels and ten Demons with amazing powers, some of which are sealed within humans. They are being searched for by the Stea Government (Angels) and the Zenom Syndicate (Demons) who want to insert them within the Kabbalah and Reverse Kabbalah, that are found on the North and South Pole respectively. A legend tells that when either Kabbalah is filled, a super weapon called the Legendary O-Part will be awoken.
Protagonists
Jio Freed
is the thirteen-year-old protagonist with half-black, half-white hair, a very long red scarf and dreams of world domination. He has great battle skill, an obsession with money and is not quick to show his feelings, often hiding them or blaming other factors. He meets Ruby, a young treasure hunter, and agrees to become her bodyguard. Jio started his life without friends, being picked on and beaten by others. The people in his village forced him to leave after the death of his only friend's, Jin, parents for which he was blamed. He was trained in the wild by a wolf named Zero for a year, and draws fangs on his cheeks in tribute to his master, before being chased away to complete his dream of world domination. After gaining Ruby and Ball as friends, and training under Kirin, Jio becomes more trustful of people and slowly breaks away from his dream of world domination, choosing to be more helpful and caring of others. This new outlook quickly gains more friends such as Mr. Wick and Mrs. Vercil, who he sees as his father and mother, never having known his real parents; Jio is emotionally crushed when they are killed by Kujaku in cold blood.
His main O-Part is a boomerang called (C rank) which doubles the energy it receives. He named it after his master Zero. After being repaired by Kirin, it is upgraded to the three-winged (B rank), which triples the power. Jio is the container of Demon No. 1i, , and seems unaware of Satan's existence, not knowing why the people in the village hated him. But during Jio's second fight with Wise Yury, Satan informs Jio that his body, "the vessel", is ready and grants him the . Appearing on the palm of Jio's left hand and reading the number 666, it is an O-Part with the Effect of Energy Absorption. While the mark allows Jio to absorb and use another O.P.T. or Demon's ability, it also gives more and more control of his body to Satan.
During their fight on Rock Bird, Satan and Jio take a fatal wound from Cross and Metatron. In order to survive, Satan absorbs Ruby's soul into Jio. Ruby stays inside of Jio to protect him against Satan's control, and he is separated from his friends during the fall of Rock Bird. Four years later, Jio has become the leader of the Cyclopian village and his O-Part has again been updated, this time to , another boomerang-type weapon that reacts to the amount of hatred in one's heart and changes shape and size accordingly. Jio is discovered by Ball and rejoins his group to rescue Ruby from Stea Government HQ. After reuniting with Ruby, the Orphan crew then head for Zenom Syndicate HQ where Jio ultimately defeats Amaterasu Miko, who has initiated Armageddon. It is then revealed that all of the Angels and Demons, and Shin came from a planet called Eden, where 72 scientists tried to harness all the energy of the universe. To accomplish this task, they created the two Kabballahs and Shin, which have the power to absorb energy in the form of information. 20 scientists were in charge of categories of information and eventually evolved into the 20 Angels and Demons based on their category. The scientist that became Satan desired all of the energy for himself and began absorbing everything, but researchers Adam and Eve foresaw this and created a different device called Freedom. When he entered this program, Satan became trapped inside it; Jio Freed. Jio finally defeats the Satan inside him and gains control of Shin, which he warps to an uninhabited planet.