According to his widow Yasuyo, Machii was born Jeong Geon-yeong, a first-generation Korean of Minami-Sakuma Cho, Shiba Ward, Tokyo, Empire of Japan.

[4] Machii's vast empire included tourism, entertainment, bars and restaurants, prostitution, and oil importing.

More importantly, he brokered deals between the Korean government and the yakuza that allowed Japanese criminals to set up rackets in Korea.

[3] The Toa Yuai Jigyo Kumiai, commonly known as the Toa-kai, is still an active yakuza gang in Japan with an estimated membership of 1,000.

In the late 20th Century, following South Korea's increasing demand for travel due to the country's economic growth, the Busan-Shimonoseki Pugwan Ferry company attempted to expand into the Kyushu island, however the project was abandoned – several articles dated at that time reveal that nearly 70 Toa-kai members were shot or stabbed within a week in Tokyo, and it was strongly believed that the perpetrators, from the underworld, were those belonging to the Kudo-kai (controlling the Kokura Port) or the Dojin-kai (controlling most ports in western Kyushu).

Speculation exists that if Machii were active, this would never happen; at that time, the Toa-kai was headed by Morihiro Okita, the third-generation president with a bad reputation among the members due to his poor leadership.