20XX A.D. Japan is plagued by evil spirits that dwell in the shadows.

The only thing preventing chaos between spirits and humans
is an implicit agreement to "live and let live", but corrupt organisations
make deals with the demons. Crime syndicates go supernatural.

The nation is in decline, and those who walk the path of goodness
don't last long in a society of rampant heresy and sin.

Thus, the government empowers certain individuals to fight fire with fire.
Agents may do evil... against evil... in the name of good. Exorcists with a license to kill.
They are called the Taimanin.
Source: DLsite