In 1911 he graduated from the Philosophy Section, Tokyo University.
In 1911 was appointed director of the Investigation Bureau, South Manchuria Railway Company. Shumei Okawa later founded the Yuzonsha Society and Jimmukai Society, nationalistic political groups. He took part in the socalled March Affair (1931) which aimed at establishment of a military regime. He participated in the May 15 Incident (1932) in which Prime Minister Tsuyoshi Inukai was assassinated by young military officers. He was arrested the following year and released (1935). While on trial as a Class-A war criminal at the International Military Tribune for the Far East, he became insane and his case was dropped by the tribunal. He was cured subsequently and has been devoted to writing.