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.

An employee of Daikin Industries Ltd works the production line of outdoor air conditioning units at the company's Kusatsu factory in Shiga prefecture, western Japan March 20, 2015. As Japan heads into the season of peak demand for room air-conditioners, Daikin managers have been tasked with figuring out how to boost output by some 20 percent at the 45-year-old Kusatsu plant that six years ago the company had almost given up on as unprofitable. (Photo by Yuya Shino/Reuters)

A rickshaw man runs under the blooming cherry blossoms in Tokyo, Sunday, March 29, 2015. (Photo by Shizuo Kambayashi/AP Photo)

Women in yukatas, or casual summer kimonos, take their selfie in front of paper lanterns during the annual Mitama Festival at the Yasukuni Shrine, where more than 2.4 million war dead are enshrined, in Tokyo, Japan July 13, 2017. (Photo by Kim Kyung-Hoon/Reuters)

Dog groomers participate in a contest at the “Interpets” international pet fair in Tokyo, Japan, 01 April 2021. (Photo by Franck Robichon/EPA/EFE)

Waka Tsukiyama and Sayaka Unagi compete during the Women's Pro-Wrestling “Stardom” at Korakuen Hall on September 06, 2021 in Tokyo, Japan. (Photo by Etsuo Hara/Getty Images)

A sommelier serves the glass with 2021 Beaujolais Nouveau wine of a young woman bathing in a red colored hot water bath, on the day of the Beaujolais Nouveau official release, at Hakone Kowakien Yunessun hot spring resort in Hakone, Japan, 18 November 2021. Japan is a major market for the Beaujolais Nouveau. However, the country's total Beaujolais Nouveau imports are expected to fall by 20 per cent from 2019 to around 3,6 million bottles, amid the ongoing coronavirus pandemic. (Photo by Franck Robichon/EPA/EFE)