When Taoka inherited the title of kumicho, it was merely a local family with only a few dozen members. It was Taoka who made Yamaguchi-gumi the world's largest criminal organization. He urged his underlings to have legitimate businesses and allowed them to have their own family, which became a kind of subsidiary family of Yamaguchi-gumi. He also created a structural system in the family. Wakagashira were elected as underbosses to the kumicho and some of powerful members were elected as wakagashira-hosa (deputy underbosses).[citation needed]
4th kumicho (1984–1985): Masahisa Takenaka
After the death of Taoka, the heir apparent wakagashira Kenichi Yamamoto (kumicho of the Yamaken-gumi) was serving a prison sentence. He died of liver failure shortly afterward. Fumiko Taoka, Kazuo Taoka's wife, stepped forward to fill the leadership void until a new kumicho could be selected by a council of eight top-level bosses. In 1984, the elders chose Masahisa Takenaka (kumicho of the Takenaka-gumi) to be the fourth kumicho of Yamaguchi-gumi. One of the other contenders, Hiroshi Yamamoto (kumicho 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-kumicho Kazuo Nakanishi (kumicho of the Nakanishi-gumi) and wakagashira Yoshinori Watanabe (kumicho of the Yamaken-gumi) briefly took the leadership role until 1989.
5th kumicho (1989–2005): Yoshinori Watanabe
The Yama-Ichi War ended with retirement of Hiroshi Yamamoto which was arbitrated by one of the most respected bosses Seijo Inagawa. After that, the clan elected wakagashira Yoshinori Watanabe as 5th kumicho of the organization. Masaru Takumi (kumicho of Takumi-gumi) was elected as wakagashira. He was so powerful and respected within the organization that his influence overshadowed that of kumicho to some extent.
6th kumicho (2005–present): Shinobu Tsukasa (real name: Kenichi Shinoda)
In 1997, then powerful wakagashira Masaru Takumi was assassinated by underlings of then wakagashira-hosa (deputy underboss) Taro Nakano. After this assassination, they were unable to choose a new wakagashira for more than eight years. As a result, leadership of the organization became weaker. Finally, in 2005, wakagashira-hosa Shinobu Tsukasa (then kumicho of the Hirota-gumi) was chosen as new wakagashira and shortly afterward, in August 2005, Tsukasa inherited the position of the 6th kumicho of the Yamaguchi-gumi.
Watanabe retired to private life—rather uncommon in Yakuza circles, as bosses usually do not retire until their death.[5] Under Tsukasa's leadership, the 6th Yamaguchi-gumi has resumed expansion. Kiyoshi Takayama, kumicho of the Kodo-kai, was elected as wakagashira. They absorbed the Tokyo-based gang Kokusui-kai, thus acquiring lucrative turf in the capital. Tsukasa was imprisoned in December 2005 for illegal gun possession, and was released in April 2011 after serving nearly six years in jail.[6][7]