Windwalker was trained as a monk.  Peaceful and calm he studied and was content.
When he ended up in the city he was captured by criminal organization and experimented on.
They inserted a device at top of his spine.
The device allowed him to regulate his body using his monk training.
This increased his strength and reactions.  Others they tried use this on had died.
It also gave them control over him as they could shut down and paradise him.
The criminal organization could now use his training as monk in unarmed combat and bow for their ends.
Windwalker served the criminal organization but set about learning technology that controlled him.
After what seemed to be a lifetime, he gained access to technology and manipulated events to override the device and gain control of himself.  However the device could not be removed as kill him do so.
Although he know not his fault all things he did for the criminal organization, he has decide to balance what he done by becoming Windwalker and taken up life of crime fighting.
To earn basic living he teaches self defense and meditation classes.