Shozo Hirono at the Kaito-gumi headquarters
The Kaito-gumi was a Japanese yakuza family based in Hiroshima, Hiroshima Prefecture, Japan. It was the most powerful family in the city by the late 1940s, and, in 1949, it was called upon to mediate the dispute between the feuding Yamamori-gumi and the Doi-gumi. After the Yamamori-gumi assassinated the latter family's patriarch Kiyoshi Doi at the Kaito-gumi headquarters, the Kaito-gumi allied with the Doi-gumi against the Yamamori-gumi, but they made peace with the Yamamori-gumi on the Doi-gumi's defeat that same year. In 1956, the Yamamori-gumi captain Tetsuya Sakai attempted to form an alliance with the Kaito-gumi and possibly form his own organization, but he was assassinated by a rival faction within his family before he could do so.