In a country very much like present-day Japan, governed by an emperor who rules with an iron fist, a dark disease known as "BT" is spreading out-of-control. All those infected with BT will be overtaken by an insatiable desire to kill.

The emperor charges a group of skilled men with the responsibility of eliminating all "BT carriers." Among them are two brothers with cursed blood running through their veins. Though they appear fearless, there is one thing even they seem to dread: the Yomizakura, a mark of death which serves as a chain binding them to their traumatic childhoods.