A devastating conflict between humans and monsters took place during the 20th century. In its aftermath, the monsters secretly dominate the world, instilling fear while staying largely out of sight. A young boy named Bokka reflects on the past, wondering what became of the Meros Warriors who once bravely fought the demons. He soon encounters Kurofune and learns about the Meros' power and the I-bar machines they pilot into battle. Only these warriors can perceive the Melody of Oblivion—a phantom girl hidden away, awaiting rescue to become humanity's savior. During a clash between Kurofune and a demon, Bokka makes an astonishing discovery: he too can hear that melody, something beyond his wildest dreams. As he travels, Bokka encounters numerous monsters, their agents, friends, and companions, gradually uncovering the full extent of his newfound abilities. He must continue fighting evil, hoping to free Boukyaku no Senritsu and liberate a world that has forgotten its once beautiful melody.
