Ten years ago, an inscrutable and abnormal territory known as Hell's Gate appeared in Tokyo and altered the sky and wreaked havoc on the landscape. The heavenly bodies disappeared, replaced by false stars. During this time, people who possess various special abilities emerged. Kept secret from the knowledge of the masses, these individuals, known as Contractors, are able to murder in cold blood. Various nations around the world use Contractors as spies and agents, often resulting in violent battles for information.
Hei "The Black Ripper" is one of the most powerful of these psychic agents. Working for one of the many rival Organizations/Nations vying to unlock the mysteries of Hell's Gate, Hei along with his blind associate, Yin, must fight against the other Contractors in various dangerous, action-packed missions.