山本博
In 1984, the elders chose Masahisa Takenaka ("kumichō" of the Takenaka-gumi) to be the fourth "kumichō" of Yamaguchi-gumi. One of the other contenders, Hiroshi Yamamoto ("kumichō" of the Yamahiro-gumi), broke away from Yamaguchi-gumi with many of its powerful members and more than 3,000 of its soldiers to form the Ichiwa-kai. A bitter rivalry existed between the two groups, which led to an all-out war (the Yama-Ichi War) after the Ichiwa-kai's 1985 assassination of Takenaka and "wakahashira" Katsumasa Nakayama. During the war, acting-"kumichō" Kazuo Nakanishi ("kumichō" of the Nakanishi-gumi) and "wakagashira" Yoshinori Watanabe ("kumichō" of the Yamaken-gumi) briefly took the leadership role until 1989.