From a very young age, Hakushi has been sheltered and hidden from the world by his parents despite their family's deep ties within the village known as Amegakure. Upon turning the rather swift and elegant age of eight however, this young boys life changed for what seemed to be the worse. The young boy was taken from his parents, and sold into a unique form of slavery which promoted to development and harnessing of bacterial and viral materials in war-like scenerios.
After a few years of experimentation, his body was put through various trials and out of about one-hundred other 'participants' he was the only to survive. The details and precise measures taken within these trials was locked away and hidden forever once the Kirigakure raided and took over the facility for their own personal use.
Shortly after discovering the young boy within the facility, they inspected him and saw no real reason to label him exempt from Nina Academy enrollment so they figured they might as well see where he stands. A few dozen classes, tests and exams later he was a trained Genin of the Kirigakure and of course this wasn't the end of his story.
A few months of being a ninja, and he was given his first assignment to scout the out-lying lands and give an accurate report of their populace. He never returned to his 'home' village and due to his obvious lack of skill he was written off as a causality of circumstance.