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.P.T., and inside him sleeps a demon of incredible ferocity. He meets up with a girl named Ruby, and together they decide to embark on a dangerous quest to discover as many O-Parts as they can. Will Jio help Ruby realize her dream of becoming a world famous treasure hunter? More importantly, will Ruby help Jio realize his dream--of world domination?!
The government of Stea is on the hunt for a pair of rogue O-Parts users. Armed with a high-class piece of weaponry, this devious pair of lawbreaking brothers is ready to hit Stea's special squad with everything they have. Will an even more powerful O.P.T. be able to stop their violence? Later, Jio's past comes into focus when more is revealed about the origin of his unique O-Part and the identity of his master: a powerful wolf named Zero!
Jio and his new friend Ball, a member of the resistance group fighting against the corrupt Governor Jaga, are in deep trouble. They've successfully broken into Jaga's lair, but are they strong enough to survive a battle with the notorious criminal Wise Yury? Later, Ruby learns more about her father and the secret origin of the pendant he gave her before his mysterious disappearance. Could Ruby's seemingly unimpressive trinket actually be one of the most powerful O-Parts of all?!
Jio's friend Ball always dreamed of being strong--strong enough to help the resistance movement stop the maniacal governor Jaga who has a stranglehold on his hometown, and strong enough to defend his friends and his sister. Now that he too is an O.P.T., it looks like Ball might stand a chance! Can he, a novice when it comes to O-Parts, defeat a powerful member of the Zenom syndicate single-handed?
To defeat the legendary O-Part Mexis, Jio was forced to make a dangerous pact with the evil spirit that dwells deep within his heart. Now that the time has come to resume his battle with the man responsible for shattering his old O-Part--Wise Yury, the Crimson Magician--will Jio's newfound strength aid him in stopping this powerful O.P.T., or will his eternal soul be lost in the process?
Now that peace has returned to Entotsu City, Jio, Ruby and Ball strike out for the Dastom Ruins where they are told to search for a man named Wick--but the revelations Wick is about to share with them will be anything but easy to swallow. Is it true that O-Parts are originally from another planet far, far away? And is Jio now strong enough to survive his next run-in with the ruthless Zenom Syndicate?
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?
The Olympia tournament has begun, and Jio is ready to do battle in the preliminary rounds! But his opponent Anna has some wily tricks up her sleeve...as does Ikaros, the leader of Rock Bird! The action heats up when the tournament moves to a spherical arena where participants can fight in zero gravity! Along the way, Jio meets some more of his fellow contestants, including the steadfast Kite and his ailing friend Yuria. Can Jio win the tournament and help his newfound friends?
Yuria's battle with Python Jack continues, and Python Jack seems to have the upper hand. But Yuria has a trick up her sleeve. Unfortunately, she may need to give up her soul to use it... Meanwhile, Jio bumps into a childhood friend--and some unpleasant memories--he thought he'd never see again. Have the demons of the past been laid to rest, or is there still bad blood between the two?
As the battle between Shuri and Jin intensifies, Anna and Kite remain imprisoned. Meanwhile, Jio and Ball prepare for their battle. Jio is an amazing O.P.T., and Ball is stronger than anyone expected...but their opponent is fierce. Will Jio have to rely on the dark power inside him in order to win?
Our heroes head off to save Ruby but are thwarted by two monstrous guards! Will Ball be able to hold them off while Jio charges to Ruby's rescue? Or will Jio fail his toughest test yet when he's forced to face his own true nature?
As the Olympia tournament continues, Jio squares off against Ikaros to save Ruby. It seems like a fair fight, but Ikaros is not what he seems. Will Jio be able to handle Ikaros's true form? Meanwhile, the Zenom Syndicate moves closer to completing the Reverse Kabbalah...and Cross arrives at Olympia to take his final revenge against Satan.
Although Ruby has succeeded in saving Jio's mind from the depths of Satan, her soul remains inside Satan/Jio's body. Realizing that Jio has come back, Cross decides not to kill him. But amid the turmoil, Ruby's pendant falls into Jio's hands...and Ruby's body (without her soul) falls into the Stea Government's!
Jio and his friends boldly set out to rescue Ruby from the Stea Government headquarters. Sneaking in is easy enough, but what will happen when they are forced to face their worst foe yet--Chief of Staff Dofwa--whom even Kirin and Amidaba have as yet been unable to defeat?
After destroying Miko's robot body, Jio reunites with Ruby. They join with Ball and their other friends to search for the headquarters of the Zenom Syndicate, which has been making progress in capturing the Demons of the Reverse Kabbalah. However, little do they realize how all-consuming their search will become!
Swallowed by Nehema, the largest of all Demon Recipes, Jio and his friends make their perilous way through the various ruins and monuments they find inside. Meanwhile, Kirin comes face to face with his nemesis, his twin brother Kujaku, and the reason for the enmity between these siblings is revealed!
Separated into various groups and confronting a variety of threats, Jio and his friends hope they're reaching the end of their struggle to break the Zenom Syndicate. It's been a tough final push, and as they know only too well, no fight is over until it's over!
The leader of the Zenom Syndicate has acquired the Kabbalah and the Reverse Kabbalah, and he is very close to realizing his dream of completing them. Miko, leader of the Stea Government, sees her dream of ultimate world unification about to come true as well. Both, however, face an ultimate challenge from Jio and his alter ego, Satan!