Sword Gai: The Animation Season 1

A weapon that has drawn the blood of countless victims becomes legend, and at times takes on a life of its own. When such a weapon's human host is filled with hate and murderous intent, he becomes a demonic combination of weapon and man that thirsts only for slaughter. An organization has faced these dangerous beings over the centuries. A young man named Gai is destined to live as a weapon. As humans are enthralled by their weapons' power, epic battles unfold with the fate of humanity in the balance in this battle action fantasy.