[citation needed] The most famous kuromaku, or behind-the-scenes power broker, of the 20th century, he was active in Japan's political arena and criminal underworld from the 1930s to the 1970s, and became enormously wealthy through his involvement in smuggling operations.

In 1933, Kodama formed his own ultranationalist group called the Independent Youth Society (独立青年社, Dokuritsu Seinensha), which planned to assassinate various Japanese politicians.

[6] Its main activity was opium export from Japan to Korea and Manchuria to break the resistance of the local population against the Japanese rule.

He was released from Fuchū prison at the instigation of Doihara, by this time promoted to major general, just prior to the outbreak of the Second Sino-Japanese War in April 1937.

[citation needed] With these resources, Kodama was able to use what he described as "self-sacrificing youth"[9] to engage in large-scale plunder in Manchuria and China and sell the stolen goods at a high profit in Japan.

Shortly after the announcement of the unconditional surrender of Japan on August 15, 1945, he witnessed the ritual suicide of Admiral Ōnishi, but was subsequently unable to bring himself to commit seppuku.

[17] Kodama also formed a close relationship with fellow suspected Class-A war criminal (and future prime minister) Nobusuke Kishi.

[18][7] Since he had a lot of time, Kodama was able to keep himself up to date on current events and far-reaching political changes in East Asia in all available daily newspapers.

Kodama, being a right-wing ultranationalist, eagerly fulfilled his end of the bargain, using his fortune and network of contacts to quell labor disputes, root out Communist sympathizers and otherwise fight socialist activities in Japan.

[23] He began to use the fortune he had accumulated in China and subsequently hidden, which supposedly amounted to 70 million yen (not including the platinum and diamonds he spirited away),[24] to covertly influence electoral politics in postwar Japan.

An example of his role as fixer was the planned state visit by US President Dwight D. Eisenhower in 1960, in connection with the revision of U.S.-Japan Security Treaty (known as Anpo in Japanese), intended to cement the U.S.-Japan alliance.

[26] As the protests dramatically escalated in June 1960, now-Prime Minister Nobusuke Kishi asked his old friend Kodama to organize right-wing thugs and yakuza gangsters as a private police force to secure the streets for Eisenhower's visit.

[18] Kodama obliged, using his right-wing connections to prepare a "Welcoming Ike to Japan Mobilization Plan" which he claimed would be able to put nearly 150,000 young rightists on the streets in order to "protect" President Eisenhower from left-wing protesters.

[31][32] Zen'ai Kaigi carried out a variety of counter-protest activities in support of the conservative Kishi government, and by the end of the protests had grown to include more than 100 organizations.

[32] In this way, the 1960 Anpo protests helped cement the interlocking relationships between right-wing nationalists, yakuza gangsters, and conservative political interests, with Kodama playing a starring role.

[18] In April 1961, Kodama formed his own sub-faction within the Zen'ai Kaigi called Seinen Shiso Kenkyukai (Society for the Study of Youth Ideology), which represented a hard core within the umbrella organization, mainly yakuza.

[citation needed] One of the victims of this organization was the journalist Hisatomo Takemori (久友竹森), whose book entitled Black Money was not published after multiple threats.

[citation needed] He owned shares in Hisayuki Machii's Ginza nightclub empire, a shipping company, a baseball team, a film studio, and several sports magazines.

[2][42] After the Lockheed scandal, disillusioned ultranationalist Roman Porno film actor Mitsuyasu Maeno attempted to assassinate Kodama by flying a Piper PA-28 Cherokee plane kamikaze-style into his mansion in Setagaya Ward's Todoroki.