The story took place in a city which never slept. A city of alcohol, drugs and sex. A city of pleasure and desire.

In that city lived an assassin called D, whose name or nationality were unknown. The underworld feared him, calling him "the Angel of Death".

One day, D received a request from a mysterious girl, Shinmei Tsubasa, who claimed to be the daughter of the Head of the Shinmei Ecology Lab. The lab was burnt down three days ago and everyone, Tsubasa included, was supposed to be dead. The girl said her life was in danger and wanted D to become her bodyguard.