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)

People watch the Pikachu parade which is a part of the 2023 Pokémon World Championships, at Grand Mall Park in Yokohama on August 11, 2023. (Photo by Philip Fong/AFP Photo)

A dog walks on the street as it snows in Kyoto on January 25, 2024. (Photo by Philip Fong/AFP Photo)

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)

People view live owls at, Owl's Forest which is located on the bottom floor of a building along a bustling street in the Harajuku area on Friday November 04, 2016 in Tokyo, Japan. Visitors can pet owls at the business. It is located next to one of Tokyo's many cat cafes. (Photo by Matt McClain/The Washington Post)

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)

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.