A young man named Akiyuki is a victim of a terrorist attack perpetrated on his peaceful island during wartime. As a result of the attack, he is imbued with an indefinable entity known as a Hiruko and becomes Xam'd. Akiyuki is unwillingly endowed with great powers and must learn to live in symbiosis with the Hiruko. If he does not, the Hiruko will take over his soul and turn him to stone. Akiyuki's family and friends become intertwined in the war which is raging between the northern and southern islands of their homeland.