Ōkunoshima Poison Gas Island

ÅŒkunoshima is a small island in the Seto Inland Sea off Takehara, Hiroshima Prefecture. From 1929 the Imperial Japanese Army operated a secret chemical-weapons factory here, producing mustard gas and other poison agents; to hide the work, the island was erased from published maps. Thousands of people, including mobilised students and local labourers, worked in hazardous conditions, and many suffered severe, lasting injury from exposure. Production continued through the Second World War until Japan's defeat in 1945.

Redeveloped for recreation after the war, the island is now widely known as "Rabbit Island" for its many feral rabbits. Its crumbling gun batteries, ruined power station and empty gas-storage bunkers give parts of it a sombre, uneasy feel, and some visitors describe an unusual heaviness among the concrete shells. Such impressions are personal responses to a scarred wartime landscape rather than evidence of anything supernatural.

The ÅŒkunoshima Poison Gas Museum, opened in 1988, documents the suffering of those affected and argues for the abolition of chemical weapons. With the memorial to the dead and the surviving ruins, it makes the island a place of genuine historical importance, a quiet warning about the human cost of chemical warfare, to be visited thoughtfully rather than for spectacle.

Ōkunoshima is reached by a short ferry from Tadanoumi port near Tadanoumi Station and is developed around a Kyūkamura resort with a hotel, camping and visitor facilities; the island's rabbits and Inland Sea views make it a popular day trip. The Ōkunoshima Poison Gas Museum is open daily, typically 9:00–16:00, with a modest admission fee and closure over the New Year period.

The wartime ruins, including batteries, the power plant and storage sites, can be seen on foot along the island's paths, with interpretive signage explaining their history. Visitors are asked to treat the site with respect as a place where many people were harmed, and to check current ferry times, museum hours and any access restrictions before travelling.