Gennosuke began life in difficult fashion, he and his mother following his father on a mission of revenge on behalf of Lady Asano of clan Shirageta. Gen was taught how to fight by his father, but came to resent him because of his cold samurai ways.

When Gen turned thirteen, his mother now dead, he struck out on his own, leaving his father to continue his vendetta alone. He soon discovered that his father's kenjutsu training came in handy and he turned his hand to bounty hunting.

Gen 'befriended' Usagi while attempting to con him into helping him kill a group of bandits. Gen is extremely good at his chosen profession, and while he claims to have no sense of honour there is something about Gen that makes those that are his friends convinced that he is neither heartless or stupid. He is a loyal to his money, but no matter how much he denies it, he is loyal to his friends first.