In 1920s Tokyo, a surge in vampires throws the city into chaos, fueled by a black market artificial blood substitute.
To combat this threat, the Japanese military forms Code Zero, a specialized unit composed of both humans and vampires.
Led by Colonel Maeda, Code Zero is tasked with hunting down vampires and stopping the spread of the artificial blood.
However, the unit faces internal struggles as its vampire members grapple with their new identities and the pressures of being both hunter and hunted.
The team must overcome these challenges and suppress the vampire threat before it overwhelms the city and consumes them all.