Very much like other yakuza groups based in the northern Kyushu region such as the
Taishu-kai and
Kudo-kai, the Dojin-kai has been noted for its aggressive and violent nature, causing numerous bloody conflicts with other yakuza groups. Notable ones include the
Yama-Michi War (,
1986–1987), where the organization substantially expelled the largest known
Yamaguchi-gumi syndicate from the northern Kyushu area. Another notable one is a brief conflict that occurred in 1983, with the
Kanto-based large yakuza syndicate
Sumiyoshi Union, in which a majority of Dojin members moved to Tokyo and had been hiding out around Tokyo with the plan of slaying all of the Union's 76 senior bosses until the Union made a conceding offer of peaceful resolution (
teuchi). The Dojin-kai is noted for having been isolated in the yakuza world in an uncanny way, in contrast to most other yakuza organizations which usually have at least one ally (
sakazuki-shared "brother" organization). In one notable anecdote, during the time of the
Yama-Michi War, there were several offers of help from other organizations but the Dojin-kai reportedly rejected all of them. The Dojin-kai is a member of an anti-
Yamaguchi fraternal federation, the Yonsha-kai, formed with three other northern-Kyushu based independent yakuza syndicates, the
Kudo-kai,
Taishu-kai and Kumamoto-kai. More than five Dojin offices in Kurume and Fukuoka were attacked with bombs and firearms on May 21 of that year, and soon after that, on 24th, Seido-kai's Jinsei group headquarters office in
Chikugo was totally destroyed, apparently by Dojin-kai's bombs. On June 13, 2007, Zenji Tsurumaru was killed. On June 19, Hidenori Irie was killed. On August 18, the leader of Dojin-kai, Yoshihisa Onaka was killed. On November 8, a civilian Hiroshi Miyamoto was killed by mistake while receiving treatment at a hospital. On November 12, Shigeki Koga was killed. On November 27, Yoshikazu Matsuo, one of the chairmen, and his driver were killed. Both groups announced a cease-fire on December 18 and on February 5, 2008, the war reportedly ended. The Fukuoka Prefectural Police discovered that the Seido-kai built a
cenotaph in July 2009 in Omuta to pay tribute to their casualties. The names inscribed on its surface not only included those of Seido-kai members but also included those of Dojin-kai members. This cenotaph, however, disappeared by early 2011. The Dojin-Seido war has been escalating since the late 2000s, especially in 2011, when they started using military machine guns and tossing grenades at each other. Many Seido members have escaped from Kyushu since the late 2000s, building an eight-story bulletproof building in
Taito, Tokyo as their new base. The first Seido president, Chojiro Murakami, was arrested in
Ibaraki Prefecture. Kazuma Umeki, one of the top underbosses in the Seido-kai, was attacked with a 10-ton dump truck driven by a Dojin yakuza. In April 2011, two Seido seniors were shot with a revolver in Imari by a Dojin hitman, and Sueharu Matsunaga, the head of the Seido's Matsunaga group, was killed with a bomb. ==Activities==