Ōkunoshima played a key role during World War II as a poison gas factory for much of the chemical warfare that was carried out in China.

Nevertheless, Japan went to great lengths to keep the chemical munitions plant a secret, even going so far as to remove records of the island from some maps.

Under the jurisdiction of the Japanese military, the local fish preservation processor was converted into a toxic gas reactor.

Working conditions were harsh and many suffered from toxic-exposure related illnesses due to inadequate safety equipment.

People were told to be silent about the project, and several decades would pass before victims from the plant were given government aid for treatment.

"[6] As expressed by its curator, Murakami Hatsuichi, to The New York Times, "My hope is that people will see the museum in Hiroshima City and also this one, so they will learn that we [Japanese] were both victims and aggressors in the war.

"[7] The small museum is only two rooms large and provides a basic overview of the construction of the chemical plant, working conditions, and the effects of poison gas on humans.

Access to Ōkunoshima from mainland Japan is via the San'yō Shinkansen train to Mihara Station (only the Kodama stops there).