The Black Book Club are a consortium of wealthy mobsters and businessman who traffic demons as slaves and the overarching antagonists of Yu Yu Hakusho. They were formed after a group of mob bosses learned of the Demon World and pillaged it, kidnapping innocent demons to be sold as slaves and torturing and killing them for fun. They run numerous mansions where demons are held and gruesomely tortured for the amusement of their members.
The Black Book Club began as a criminal organization that discovered the existence of the Demon World and used the power of eight psychics to keep open a small portal which led to Demon World. Using this portal, the Black Book Club was able to enter the Demon World and began massacring peaceful demons while kidnapping others to be sold as slaves on the black market. Soon, the Black Book Club's underground slave trade of demons, overseen by Sakyo, became immensely profitable and many of the top members of the club developed net worths in the trillions. In fact, the club was said to have assets that dwarfed the gross domestic profit of Japan. The club also set up mansions to hold feasts for their members where enslaved demons were subject to horrific tortures and killed gruesomely for the sadistic pleasure of those attending. After Sakyo began a plan to open a permanent portal to the Demon World, and cause the destruction of the planet in the process, other members the Black Book Club attempted to kill Sakyo but were killed instead by Team Toguro.
Though the Black Book Club was ended, the effects of their crimes remained. The sight of one of their Feasts was enough to drive Spirit Detective Shinobu Sensui into misanthropy, leading him to kill everyone present at it.
- Gonzo Tarukane - Founder
- Team Toguro