A performer dressed as a zombie performs inside a “Zombie Shinkansen” bullet train bound for Osaka from Tokyo, inspired by the South Korean movie “Train to Busan” ahead of the Halloween season, Japan, on October 19, 2024. (Photo by Kim Kyung-Hoon/Reuters)

People are walking with umbrellas on a snow-covered street during the first snowfall of the year in Tokyo, Japan, on February 5, 2024. (Photo by Jerome Gilles/NurPhoto/Rex Features/Shutterstock)

A participant marches during the Tokyo Rainbow Pride parade, celebrating advances in LGBTQ+ rights and calling for marriage equality, in Tokyo, Japan on April 21, 2024. (Photo by Issei Kato/Reuters)

Fumie Takino, 89, founder of a senior cheer squad called Japan Pom Pom, and other members pose for commemorative photos before filming a dance routine for an online performance in Tokyo, Japan, April 12, 2021. “It's dancing; moving your body is nice”, Takino said. “And the costumes are unbelievably showy. Some people join just so they can wear them”. (Photo by Kim Kyung-Hoon/Reuters)

Visitors take masks off to take pictures as hydrangea flowers are fully blooming at Meigetsu-in Buddhist temple Friday, June 11, 2021, in Kamakura, south of Tokyo. (Photo by Kiichiro Sato/AP Photo)

A tourist cools off in front of a misting fan near a venue of the Hozuki-Ichi (Japanese lantern plant fair), at Sensoji temple, in Tokyo, Japan, on July 10, 2025. (Photo by Kim Kyung-Hoon/Reuters)

Participants carry a portable shrine, or mikoshi, into the sea during a purification rite at the annual Kurihama Sumiyoshi Shrine Festival at Kurihama, Yokosuka city, south of Tokyo Sunday, July 27, 2025. (Photo by Eugene Hoshiko/AP Photo)

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.