His name is Goran. He's half angel, half devil and basically a taboo. That's the reason he's in chains and has to be kept locked up in a secret location on Earth.
...I know, I know. Someone's been on the ol' Saiyuki.
edit: I did a little more to it in a PM to Maru-san so...
Goran is just a really sweet innocent character and he doesn't know what he's done wrong just that he needs to be locked up for it. So he thinks he's evil and when this guy he makes friends with tries to free him, he alerts the guards and the guy gets killed. Then the main story starts with someone finding him after Goran has been forgotten by Heaven and Hell and all the guards have gone.
