Inoue was born Inoue Shirō (later adopting the name Akira and then Nissho, lit. “Called by the Sun”) in Kawaba, Gunma Prefecture, in 1887, the son of a rural doctor. Educated at Toyo Cooperative (now Takushoku University), he abandoned his studies and traveled to Manchuria where he spent time as a vagabond and ultimately found employment as a spy for the Japanese army. Upon his return to Japan, he became a follower of Nichiren Buddhism, a conversion led him to relocate to Miho, Shizuoka Prefecture, in order to study under the Nichiren scholar and nationalist preacher Tanaka Chigaku at his Kokuchukai Academy. Inoue soon became disillusioned with Tanaka’s teachings, however, and in 1928 he relocated to Oarai in Ibaraki Prefecture where he established his own temple, Rissho Gokokudo (立証護国堂, The Righteous National Defense Temple), which also served as a youth training center, advocating a militarist revolution in Japan. (一億人の昭和史, p.16) During this time, with the assistance of former Lord Keeper of the Privy Seal of Japan Tanaka Mitsuaki, he became acquainted with such right wing figures as Okawa Shumei and Kita Ikki, and received enthusiastic support from the young officers of the Tsuchiura Naval Base.
In 1930, Inoue abandoned Rissho Gokokudo and moved to Tokyo where he set about forming Ketsumeidan, recruiting members amongst university student radicals. (Large, “Nationalist Extremism” p.548) Ketsumeidan was officially founded in 1932, together with a group of 13 young officers including Onuma Shō and Hishinuma Goro, establishing as its goal the overthrow of the political and economic elite of the time, with the motto “One Man, One Assassination.” The group’s first wave of assassinations came in early 1932, with the shooting of former finance minister Inoue Junnosuke on February 9 and the Director General of the Mitsui zaibatsu Baron Dan Takuma on March 5, collectively known as the League of Blood Incident (血盟団事件). Inoue was arrested soon after the latter assassination, following which Koga Kiyoshi, a trusted subordinate, took over the reigns of the group and set about organizing a second wave, culminating in the May 15 assassination of Prime Minister Inukai Tsuyoshi, an event known as the May 15 Incident.
Inoue and the three Ketsumeidan gunmen were sentenced to life imprisonment in November 1934, with the rest of the arrested group members given lighter sentences. Inoue was later granted amnesty and released from prison in 1940. (一億人の昭和史, p.16). Seen as a fascist by the US occupational forces in 1947, he was once again rehabilitated upon the transition of power to the Japanese government and would remain a prominent figure in right wing activist circles in the post-war era.