Gai was born beside a woman who met her death in a forest. He was adopted by the swordsmith Amon. A few years later, Gai becomes Amon�s apprentice, and during the forging of a sword, he loses his right arm. To help him, Amon crushes the demon sword Shiryu (lit. Death Dragon) to form it into Gai�s replacement right arm. Gai then is able to fuse with the weapon on his arm, and fights against his enemies.