In Tokyo, an impenetrable field known as "Hell's Gate" appeared ten years ago. At the same time, psychics who wield paranormal powers at the cost of their conscience also emerged. Hei is one of the most powerful of these psychic agents. Along with his blind associate, Yin, he works for one of the many rival agencies vying to unlock the mysteries of Hell's Gate.

The manga follows Hei and Yin as they investigate how a Black Dandelion is giving Contractor-like powers to people who come in contact with it.

Tells the storyline between the first and second seasons of the anime.