The Kokusui-kai ("Patriotic Society") (國粹会), founded in 1958, is a Tokyo-based yakuza organization with an estimated 500 members. Despite its relatively low membership, it is widely viewed as a wealthy and successful gang, controlling Tokyo's fashionable Ginza district. (If one includes local affiliates in seven prefectures of the Kantō region, its membership is estimated at 1,050). Its oyabun, or godfather, was Kazuyoshi Kudo until his suicide in February 2007.
The gang had long been a member of the Kantō Hatsukakai, a federation of Tokyo yakuza groups opposed to the powerful, Kansai-based Yamaguchi-gumi.
This changed in August 2005, when in a surprise move, the Kokusui-kai withdrew from the Kantō alliance and became an affiliate of the Yamaguchi-gumi. The timing of the change was particularly interesting: the Yamaguchi-gumi's new godfather, Kenichi Shinoda, had been installed just weeks before and had made clear his intent to expand into the Kantō region. The merger with the Kokusui-kai, in which Shinoda became sworn brothers with Kazuyoshi Kudo in a sake-sharing ritual, was concrete evidence of the Yamaguchi's expansion.