Noborito Research Institute — Ikuta Branch (Balloon Bomb Production Facility)

The Ikuta site recorded here was the main compound of the Imperial Japanese Army's Ninth Technical Research Institute, commonly known as the Noborito Research Institute (登戸研究所). With origins in 1937 on the hills of Ikuta in Tama-ku, Kawasaki City, the facility was formally organized in 1939 as a secret-warfare research arm of the Army Science Research Institute and became the Ninth Army Technical Research Institute in 1942; the site was chosen for its elevated terrain and relative seclusion, ideal for secret military research.

The institute's First Department (第一科) was responsible for developing unconventional weapons, most notably the Fu-Go balloon bomb (ふ号兵器/風船爆弾). These hydrogen-filled balloons, roughly 10 meters in diameter, were constructed from multiple layers of washi (Japanese mulberry paper) bonded with konnyaku (devil's tongue) paste. Designed to exploit the jet stream, the balloons carried incendiary and anti-personnel bombs across the Pacific Ocean to North America — making them the world's first intercontinental weapons.

Between November 1944 and April 1945, approximately 9,300 Fu-Go balloons were launched from coastal sites at Otsu (Ibaraki), Nakoso (Fukushima), and Ichinomiya (Chiba). An estimated 300 to 1,000 reached North America, causing forest fires and, in one tragic incident at Bly, Oregon, killing six civilians — the only wartime combat deaths on the U.S. mainland. Production involved mass mobilization of female students from high schools across Japan, who were conscripted under the Women's Volunteer Labor Order to assemble the paper balloon envelopes in theaters, sumo halls, and school buildings. Workers at the Noborito facility itself included over 600 local residents.

Beyond balloon bombs, the Noborito Research Institute conducted research into radio-wave weapons (く号兵器), biological and chemical agents, espionage devices, and counterfeit currency operations targeting the Chinese Nationalist government. The Second Department handled spy equipment and sabotage tools, while the Third Department produced counterfeit Chinese yuan on an industrial scale.

After Japan's surrender on August 15, 1945, the institute's staff were ordered to destroy all records and evidence. The compound, which had grown to some 36 hectares, was used after the war by Keio University and other institutions and most of its buildings were eventually demolished. In 1950, Meiji University acquired the land and established its Ikuta Campus. Building 36 (36号棟), a reinforced concrete structure believed to have been used for research on defoliants, survived and was converted into the Meiji University Peace Education Noborito Research Institute Museum (明治大学平和教育登戸研究所資料館) in March 2010. The museum displays a 1/10-scale model of the Fu-Go balloon, balloon-making materials, espionage tools, and testimonies from former staff members. Several other wartime remnants — including concrete ammunition bunkers, fire hydrants bearing the Imperial Army star emblem, a 1943 animal memorial monument, and a row of original Himalayan cedar trees — are preserved across the campus.