Only after World War II did the secret spill: Ōkunoshima, located in the Inland Sea of Japan between Hiroshima and Shikoku, was the top-secret site for manufacturing chemical warfare. When the factories were closed down, a number of exotic wild rabbits were seen freely roaming the island. They were assumed to have been the test subjects for the chemical weapons, which the military failed to eradicate when the factory was demolished.

Japan Self-Defense Force (JSDF) soldiers and firefighters make rescue works among mountain lodges, covered with volcanic ash near the peak of Mt. Ontake, which straddles Nagano and Gifu prefectures in this September 28, 2014 photo taken and released by Kyodo. More than 30 people were feared dead on Sunday near the peak of the Japanese volcano that erupted a day earlier, sending a huge cloud of ash and rock tumbling down its slopes, while packed with hikers. (Photo by Reuters/Kyodo News)

Dancers dressed as futuristic characters perform during a show at The Robot Restaurant on June 29, 2014 in Tokyo, Japan. The now famous Robot Restaurant opened two years ago in Kabukicho area of Shinjuku at an estimated cost of 10 million U.S. dollars. Performances are held three times a day and cater mostly to foreign tourists. The cabaret style shows include bikini clad futuristic dancers, performers dressed as robots and a host of large scale robots and vehicles controlled with remotes by stage hands dressed as Ninjas. (Photo by Chris McGrath/Getty Images)

Carrying a portable shrine on their shoulders, participants all clad in traditional happi coats, parade through precincts of the Kanda Myojin shrine during the annual summer festival in Tokyo, Saturday, May 9, 2015. (Photo by Eugene Hoshiko/AP Photo)

A woman with Kimono looks at cherry trees in bloom in Shinjuku Gyoen in Tokyo, Japan on Thursday, April 4, 2024. (Photo by Noriko Hayashi for The Washington Post)

A child reacts as a family takes a break next to a cooling mist at the Sensoji temple as Japanese government issued heat stroke alerts in 39 of the country's 47 prefectures in Tokyo, Japan on July 22, 2024. (Photo by Issei Kato/Reuters)

This photo taken on March 10, 2025 shows the former disaster prevention office building in Minamisanriku Town, Miyagi Prefecture, lit up on the eve of the 14th anniversary of the 2011 earthquake and tsunami disaster. (Photo by JIJI Press/AFP Photo)

High waves batter a breakwater at a port at Kihou town in Mie prefecture, central Japan on October 6, 2014. Strong typhoon Phanfone slammed into Japan, packing gusts and huge waves that have already swept three US military officials out to sea, as it made a beeline for Tokyo. (Photo by AFP Photo/Jiji Press)