Five years have passed since Hexagon Island was first attacked by demans: humans turned horned soul-sucking demons with a fatal aversion to sunlight. In response, the government built the Hexagon Field—a sunlit city only for the privileged few. While most are left trembling in fear, some stand up against the demans' terror. One of them is Raynold "Rano" Berger, a young man determined to search for his little sister, Lucy, who disappeared on the day of the demans' invasion. Fighting alongside Rano is Dr. Jin Young-Sam, a scientist seeking to uncover the secret behind the demans' existence.

Meanwhile, a mysterious man named Lessa awakens from a long sleep. He is revered by the demans as both their god and forefather—much to his own chagrin. But when disagreements begin to surface between Lessa and the deman leader, Ares, Lessa has no other choice but to turn to Rano for help. While Lessa seems to have some reservations about working with the young hunter, the two are by far humanity's best shot at vanquishing the demans once and for all.