The Soai-kai was formed in 1945 by Toramatsu Takahashi, then a member of a Yokohama-based bakuto group named the Sasada-ikka. Originally named the "Gyosui-kai" (魚水会) as an affiliate of the Sasada-ikka, the group was renamed the "Takatora-gumi" (高寅組) and again renamed the Soai-kai in 1955 when the group became independent from the Sasada-ikka.[3]