Jei grew up in the poorest, most destitute section of Dublin, in a small fringe shantytown. As a child, he watched a friend's sibling die from hunger, and others he knew died from infections and diseases. His father, Frank Adanodan, was a strong man past his prime, a construction worker who was beginning to lose what meager jobs he had to younger men. He manifested his growing frustration by drinking and then beating Jei, his siblings, and their mother. Faith Adanodan was a frail, wispy woman who never stood up to him. In addition to beating her, Frank heaped verbal abuse on Faith's head, taunting her about "the bastard you've had to raise like your own flesh and blood, if you know what's good for you." Jei never understood what this meant, but noticed that after these sessions, his mother seemed to grow a bit more remote to him. Not that it particularly made a difference; half the time she seemed to be asleep or dreaming of a better life for herself, treating her children with indifference. The only thing he had to lighten an unbearable existence was the weekly visits of a young nun named Sister Ruth, who taught Sunday School. She gave him and his friends her view of a kindly, benevolent God who grieves to see us suffer and wishes nothing more than to bring us to supreme happiness in Heaven. However, Jei interpreted "God's absolute power" to mean someone akin to his father; perhaps nicer, but still ready to damn you to Hell for eternity for the slightest infraction. Jei had no hope for a better future in his lifetime, but became obsessed with honoring God's laws, in an effort to live better in the next world. He also became a sneak, spying and then telling other peoples' sins to the parish priest. He rationalized this by saying that, like an injury, one's sins cannot be cured until the doctor (or priest) knows what they are. Also, Jei himself believed that since he was helping others cure their sins and get to Heaven, he himself would get extra merit. As a result, children began to avoid the "tattletale", and Jei became very lonely. This loneliness, coupled with his obsession, served not to drive him insane, but unbalanced him enough so that what came next did push him over the edge.
One day while praying, he saw Sister Ruth herself slip into the confessional. This shocked him: since she was her role model and inspiration, he hadn't imagined she could do anything wrong. Other than him, the pews were empty, so, overcome with curiosity, he crept over to the confessional and put his ear to the door.
What he heard was a terrible secret that had occured more than ten years ago: Sister Ruth had allowed herself to be seduced by a man, a married man, then had given birth to a child by him and had allowed him to take the baby away from her. All she had done was name him James, in the hope that the name of a holy disciple of Jesus would allow the child to be better than his sinful parents. Slowly, Jei began to realize the truth: the married man was his father, and he... James... was the baby. Frank had been more cruel to Faith than he had ever guessed, forcing her to take in his bastard, and forcing her to pretend to everyone, even Jei, that he was her own. Fighting nausea, all Jei could think of was that he had to get away, had to shun this harlot. And so he ran nearly all the way home, hardly noticing where he was going, allowing habit to guide him. This was a fatal mistake, for just before he opened the door to his house, the final revelation occured to him.
He was a bastard, the product of flagrant disobedience to God's Commandments, a nun's bastard, no less. No matter what he did, how much he repented, he would always be damned to Hell. It was his own strict interpretation of God that led to this revelation, so he passionately believed it. His rage suddenly kindled out of control, and his only thought was to get revenge on those who had sentenced him to Hell before he was even born.
So, when he wrenched the door open in the first of many berserk rages, he went straight for his father, armed with only his teeth, hands, and nails. His siblings tried to restrain him, but he literally tore them apart. He then proceeded to butcher his father, for begetting him, and his mother, for perpetuating the lie and not killing him when he was an infant. He would have gone after Sister Ruth, but at this point, the magnitude of what he had just done snapped him out of his wrath. He had just one horrified glimpse of the remains of his family, with blood coating the walls of their home, before he realized that this mass murder had truly damned him to Hell forever. He staggered out into the streets of Dublin, and unable to believe what he had just done, blocked the entire episode from his memory. All his fevered brain retained was the moment when he'd stopped and taken in the carnage around him.
He wandered the streets of Dublin for a few weeks, until, purely by chance, a Japanese priest found him. The priest, who had been visiting an Irish friend, took pity on Jei and asked him to come back to Japan with him, where he knew a childless couple who would love to take Jei in. Although he didn't know why, Jei knew he desperately needed to get out of Dublin; his subconscious was afraid that the familiar setting would trigger the memories he had suppressed. So Jei went with the priest to Japan, and once there, ran away. He found work in a fish market, eating whatever scraps were thrown his way, sleeping in the street, and gradually picking up Japanese. He stole an ice pick from the fish market, and spent days pounding it flat. He then sharpened the edges, and disappeared from the fish market for good. They couldn't have cared less about the sneaky little foreigner, and never connected him to the horrible murder of a priest a few days later.
After this, Jei lived on the streets for years, moving from one place to another. Sometimes he picked up odd jobs, but inevitably lost them, because his growing insanity was beginning to come to the surface. When he was around fifteen or so (he himself utterly lost track of his own age and birthday), a twenty-something gang leader recruited him for a savage new street sport: "the Game". It basically consisted of two boys forced to fight each other virtually to the death. Jei managed to kill his opponent the first time, due to his own strength and the fact that his opponent was even more inexperienced than he. However, it probably would have been better for Jei in the long run if he had lost, because from then on, he became the "prize fighter" of the gang's team. Jei held his position as the best for a few years, but at the cost of many injuries, badly healed bones, and lacerations. Eventually, he was challenged by someone better than him, someone who beat him so savagely, Jei was left for dead.
At this point, an SS recruiter, who had been watching Jei for a while, rescued him. He was brought to the hospital, and once he healed, more or less forced to join SS. Although he had no qualms with killing, Jei didn't particularly care to join; he wanted his contact with people kept at a minimum. He would've left, but thanks to the Game, he had become utterly addicted to fighting, and being part of SS was the only readily available way to kill with impunity. He even submitted to being tied up between assignments, so that he could stay in Schwarz and continue killing. He also continued murdering the odd clergy on the side, in his quest to "get even" with God.
During their first confrontation against Weiss, when he met Sister Ruth again for the first time in years, Jei's memory was restored. He knew himself for the monster he was, but it made no difference; he enjoyed killing so much that he no longer even pretended to be an innocent. He killed Sister Ruth with no hesitation at all; in fact, it probably made him stronger, as all his talent could now be devoted to blocking out pain.
Over time, his view of God shifted from utter devotion (even brown-nosing) to hatred, to a view of himself as almost, if not as, powerful as God. He thinks of himself as an Antichrist figure, sent to Earth to wreak destruction on God's creations, especially His clergy.