Yamaguchi-gumi
The Sixth Yamaguchi-gumi (六代目山口組, Rokudaime Yamaguchi-gumi?) is Japan's largest and most infamous yakuza organization. It is named after its founder Harukichi Yamaguchi. Its origins can be traced back to a loose labor union for dockworkers in Kobe pre-WWII.
Read more about Yamaguchi-gumi.