Division Zero, a secret branch of the Tokyo Metropolitan Police Dept. specializes in investigating and infiltrating Japan's criminal underworld, devoted to using any means necessary to get the job done.

Rei, the only female officer assigned to Division Zero, a mysterious woman with no identity of her own.

When a series of assassinations occur within Tokyo's political and financial infrastructure, Detective Hayami of the Criminal Investigations Bureau suspect a group of radical revolutionaries. But at every crime scene, he runs into Rei.

Meanwhile, professional assassin Yuki is going after the killers with a vengeance. As the mystery deepens, the three cross each others' paths once too often, leading to a shocking climax.