Inagawa, son of a Meiji University graduate who fell on hard times, never attended school.
After serving in World War II, Inagawa formed the Inagawa-gumi, the predecessor to the current Inagawa-kai, in Atami, Shizuoka, in 1949.
Inagawa was regarded as an "elder statesman" of the yakuza, and a peacemaker skilled in settling disputes between rival gangs.
In the early 1960s, he headed the short-lived Kanto-kai, a federation of Kantō region gangs organized by Yoshio Kodama.
That organization's rightist philosophy was summed up by Inagawa: "We bakuto cannot walk in broad daylight", he said.