In the midst of a vampire epidemic in 1923 Tokyo sparked by illegal 'Ascra' trading, Colonel Maeda leads Code Zero, a covert vampire-hunting team formed by military vampires. Tasked with quelling the crisis and eradicating rogue vampires, they face inner struggles with their dual identities and the looming threat of disbandment. Amidst societal backlash, the unit must navigate a treacherous path to redemption or risk succumbing to their sinister instincts.