Chosei Coal Mine Disaster Site

The Chosei Coal Mine (長生炭鉱) was an undersea coal mine located off the Tokonami coast of Ube City, Yamaguchi Prefecture, facing the Seto Inland Sea. The mine began full-scale operations in 1932, with tunnels extending approximately 1.1 kilometers from shore beneath the seabed.

On February 3, 1942, the ceiling of the undersea tunnel collapsed, allowing seawater to flood the mine workings with catastrophic speed. A total of 183 miners were killed — drowned or buried alive in the flooded tunnels. Of the victims, 136 (approximately 74%) were workers from the Korean Peninsula; company records include a register of Koreans brought over under the "collective recruitment" (集団渡航) scheme, and the bereaved families and the civic group that studies the disaster regard them as victims of forced mobilization. The remaining 47 victims were Japanese workers.

The disaster was a direct consequence of reckless mining practices driven by wartime demand for coal. Safety regulations required mining at depths of at least 47 meters below the seabed, but the Chosei mine was operating at a depth of only 37 meters — a flagrant violation that management pursued to maximize coal output as the Pacific War intensified Japan's energy needs. Testimony from surviving workers indicates that Japanese miners had begun to avoid the Chosei mine due to persistent water leakage, leading to the disproportionate assignment of Korean workers to the most dangerous sections.

Because the disaster occurred shortly after the outbreak of the Pacific War, strict wartime censorship suppressed reporting of the incident. For decades afterward, the tragedy received virtually no public attention. It was not until the 1990s, when the civic group "Chosei Tanko no Mizuhijo wo Rekishi ni Kizamu Kai" (The Association to Record the Chosei Coal Mine Flooding in History, est. 1991) began investigating and publicizing the disaster, that the story reemerged into public consciousness.

Two concrete ventilation and drainage towers known as "piya" (ピーヤ) still protrude from the sea surface above the submerged mine, serving as stark physical reminders of the disaster. On the shore, two memorial monuments stand: the "Chosei Tanko Junnansha no Hi" (長生炭鉱殉難者之碑), erected in April 1982, and the more detailed "Chosei Tanko Suibotsu Jiko Giseisha Tsuitohi" (長生炭鉱水没事故犠牲者追悼碑), completed in February 2013, which lists the names of all 183 victims. In August 2025, divers working with the civic group recovered the first remains from the flooded mine — four bones confirmed as human by the Yamaguchi police — renewing calls for the Japanese government to take responsibility for recovering and repatriating the remains of the Korean victims to their families. A further dive in February 2026 recovered more remains but was suspended after one of the divers died, and in May 2026 the Japanese government announced that it and the South Korean government were cooperating on DNA identification.