Between 1927 and 1929, the Japanese military built a chemical munitions plant on Okunoshima, chosen for its isolation and distance from population centers. The island had been fortified during the Russo-Japanese War with ten coastal defense forts, and only three fishing families lived there. The military converted a local fish preservation processor into a toxic gas reactor. Workers were not told what they were manufacturing. Under harsh conditions and with inadequate safety equipment, the plant went on to produce over six kilotons of mustard gas and tear gas, used in Japan's chemical warfare during the Second Sino-Japanese War in China. Many workers suffered chronic illnesses from toxic exposure, their suffering compounded by official silence -- they were told to say nothing about the factory's purpose.

When the war ended, the cover-up continued. Documents were burned. Allied Occupation Forces disposed of the remaining gas stockpiles by dumping them at sea, burning them, or burying them on the island. Workers were instructed to remain silent, and several decades passed before the Japanese government provided medical aid to those who had suffered exposure-related illnesses. The ruins of the gas factory and the Russo-Japanese War forts still stand across the island, but entry is prohibited because the structures remain too dangerous. In 1988, the Okunoshima Poison Gas Museum opened -- a small, two-room facility whose curator, Murakami Hatsuichi, told 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 were both victims and aggressors in the war."

After the war, when the island was developed as a park, rabbits were intentionally released onto Okunoshima. The wartime rabbits -- used to test the effectiveness of the chemical weapons -- had all been euthanized when the factory was demolished and are not the ancestors of today's population. The current rabbits descended from those postwar introductions, thriving in an environment where hunting is forbidden and dogs and cats are not permitted. They have multiplied into the hundreds, approaching visitors without hesitation and crowding around anyone carrying food. In 2015, the BBC featured the island in its series Pets -- Wild at Heart, and social media turned Okunoshima into an international destination. The island is part of the Setonaikai National Park, connected to the mainland by Japan's tallest powerline crossing at 226 meters.

The Poison Gas Museum's two rooms offer a stark complement to the rabbits outside. The first room documents the factory's construction, working conditions, and the fates of the workers whose families donated personal artifacts. The second room explains how poison gas attacks the human body -- lungs, eyes, skin, heart -- illustrated with images of victims from Iraq and Iran. The museum is aimed primarily at Japanese visitors, but English summaries accompany each section. Curator Murakami's hope that visitors would understand Japan as both victim and aggressor captures the island's strange duality: a place where the cutest destination in Japan sits atop one of its darkest chapters, and where neither truth cancels the other.