Chosei Coal Mine: Breaking the Silence

Introduction

The Chosei Coal Mine was an undersea coal mine off the coast of Ube City, Yamaguchi Prefecture. On February 3, 1942, the mine flooded, killing 183 people. Among them were 136 people from the Korean Peninsula, who had been brought to Japan under the wartime labor mobilization system and forced to work in the mine.

More than eighty years have passed since the disaster. Yet the remains of more than 180 victims have never been recovered. They remain on the seabed where the mine once operated.

The Chosei Coal Mine was a site of forced labor under Japan's wartime system. People were made to carry out dangerous work there. The disaster was not inevitable: repeated violations of safety and labor regulations directly led to the flooding.

In the decades that followed, these facts were rarely spoken of in public. The disaster and its victims were treated as if they had never existed, pushed out of public memory.

Local citizens challenged this silence. For more than forty years, they have investigated what happened, recorded testimonies that might otherwise have been lost, and reached out to people in Japan and beyond. Step by step, their work led to the discovery of human remains on the seabed and to attempts to bring them back to the surface.

Even today, the Japanese government has not taken action to recover those who remain there. The harm done has yet to be fully addressed, and the Japanese government has yet to take responsibility.

To bring back even one more person, as soon as possible, from the bottom of the sea. To restore the dignity of those who were left there. To respond to the wishes of families who have waited for decades for their loved ones to return.

This exhibition was organized in the hope that more people will come to know this history, and that this knowledge will help move the Japanese government to act.

Cover: Memorial candles, representing the number of victims, surround the remains discovered during a diving survey at the Chosei Coal Mine (August 26, 2025 / Courtesy of the Association). Back cover: People working at the Piya (October 24, 2025 / Photo by Kim Jiwoon).

Organization, Editing, and Publication: Utoro Peace Memorial Museum. Cooperation: Association to Etch the Calamity of the Undersea Coal Mine Disaster into History; Isaji Yoshitaka. Korean Translation: Lee San-hyeong. Date of Publication: September 1, 2026. © 2026 Utoro Peace Memorial Museum, All Rights Reserved.

A Letter to Mother Back Home

Mother, I am now working in a coal mine in Yamaguchi Prefecture, Japan. The tunnels run beneath the sea. It is such a dangerous place that I can hear the engines of fishing boats passing overhead. Even so, I am determined to escape, no matter what it takes. Please do not worry about me. Escaping is not easy. The site is enclosed by thick pine boards nearly three meters high, with layers of barbed wire stretched beyond them. The living quarters inside are like a prisoner-of-war camp. Security is strict. We have no freedom at all. We are confined here and cannot leave. Armed guards stand at the gate, watching us at all times. If someone says they are unwell and refuses to work for even a single day, they are treated as less than animals. We are beaten, denied proper meals, and left hungry for days. I asked a Korean worker who lives here with his family to deliver this letter in secret. Because he lives with his family, he has a little more freedom to come and go. In any case, I will escape. I will return to you, Mother. I promise.Kim Wondal, who lost his life in the flooding of the Chosei Coal Mine. The letter was addressed to his mother in his hometown.

My grandmother later told me that my father had gone into town and never returned. About two months later, a handwritten letter from my father arrived from Japan. It was addressed to my grandmother…Recollection of a descendant of Kim Wondal

What Was the Chosei Coal Mine?

Like grave markers, two piya—ventilation and drainage shafts from the former Chosei Coal Mine—still rise above the surface of the sea. They are among the few traces that remain of the tunnels that once ran beneath these waters. At around 9:30 a.m. on February 3, 1942, 183 people lost their lives beneath the seabed off Ube City, Yamaguchi Prefecture. Of them, 136 were from the Korean Peninsula and 47 were Japanese. This was the Chosei Coal Mine.

The mine entrance was on land, but its tunnels extended far offshore beneath the seabed. The piya connected the surface with the tunnels below, providing ventilation and drainage essential to work inside the mine. Mining conditions at the Chosei Coal Mine were extremely dangerous. Coal was mined from shallow seams less than forty meters below the seabed, in violation of the Mining Law. One account described the conditions this way: “In some places, water leaked from the ceiling, and you could hear the fishing boats passing overhead—pon pon pon pon—as if they were connected by a telephone line.” The danger was well known locally.

At this mine, where local people avoided taking jobs, Koreans made up 75 percent of the workforce. At the time, Korean workers accounted for 9.3 percent of coal-mine workers across Yamaguchi Prefecture, making the figure at Chosei exceptionally high by comparison. The mine was sometimes known locally as the “Korean coal mine.”

Despite the known danger, the workers continued to be made to work. Coal was needed. At the time, coal was a fundamental source of energy supporting Japan's wartime system. There was intense demand for coal production. People said, “Aircraft, warships, bullets—all depend on coal,” and “A lump of coal is a lump of blood.” The Chosei Coal Mine operated within Japan's system of national mobilization, serving that demand.

The two piya of the Chosei Coal Mine (October 30, 2024, photographed by Kim Jiwoon); major coal mines in the Ube coalfield circa 1940; and the layout of the underground tunnels of the Chosei Coal Mine (courtesy of Isaji Yoshitaka).

1. The death toll of 183 was confirmed through an examination of records, including a “Roll of Those Who Died in Service” compiled by the Greater Japan Patriotic Industrial Association and memorial tablets kept at Saikōji Temple. Based on this review, South Korea's Truth Commission determined the number of victims to be 183. 2. After the accident, the mine's operator, Yorison Fuchinosuke, testified in court that the operation had violated the law. 3. Statistical data from March 1942.

A Preventable Disaster

February 3, the day of the accident, was an increased-production day known as an “ōdashi.” On such days, the required amount of coal had to be supplied, whatever the circumstances. One factor considered to have directly contributed to the accident was a mining method known as harai-bori. This involved cutting away even the coal pillars that should have been left in place to support the roof.

Water had been leaking inside the mine for several days before the accident. The danger was clear, yet the work was not stopped. Mining in violation of the Mining Law continued in the name of increased production.

The collapse occurred about 1,100 meters from the mine entrance in a straight line, out beneath the sea. With a thunderous roar, the roof gave way, and water poured into the tunnels like a waterfall. Their escape routes cut off, many workers were trapped underground and lost their lives.

This was not a natural disaster. It was a human-made disaster: the result of continuing to mine in violation of the law, despite the known danger, while giving priority to increased production over safety.

Even before then, the miners would come up from underground saying that water was leaking in places. But if they told the labor supervisors, ‘There's water coming in,’ they would be beaten. So I heard that instead they would say things like, ‘I'm not feeling well,’ or ‘I've suddenly fallen ill,’ and come back up.Testimony of Kang Bokdeok. Testimonies and Documents [2]: Father Lies Beneath the Sea, Association to Etch the Under Sea Coal Mine Disaster into History, 2014

…there was still about a kilometer and a half to go before reaching the surface, and I thought there was no way I was going to survive. … If I hadn't run, I wouldn't have made it. After I had gone a little farther, the water was already up to my waist. … At this mine, the ground was lower near the pit entrance and higher farther in. So the water that had gone farther in came rushing back, and large mine timbers came floating toward us. I climbed onto one of them. We only had another seven or eight meters to go to reach the main pit entrance and be safe, but some people died because they couldn't make it that far. When we finally got there, there was a rope hanging down, with people lined up one after another. Someone told me, ‘Grab the rope,’ and I climbed up. When I finally made it up, I was so relieved, so relieved—I just collapsed.Testimony of Lee Jongcheon. Testimonies and Documents [2]: Father Lies Beneath the Sea, Association to Etch the Calamity of the Under Sea Coal Mine Disaster into History, 2014

Welcome, everyone. As you already know, Japan is now at war. Although we are not standing on the battlefield, we have a grave responsibility to defend the home front with the sense that we too are on the front line. Large quantities of guns, artillery, ammunition, warships, and other equipment must be produced for the war. Coal is needed above all to make the materials for them. Each and every one of you who mines that coal must devote yourselves to your work with the sense that you yourselves are fighting the war. That is what it means to serve the nation through industry, and it is an act of loyalty. It may earn you bonuses for coal production or unexpectedly large sums of money. You may be able to bring your families to the Japanese mainland and live happily together, or send money home and make them happy. […] A coal mine, as long as you are careful, is truly a place where you can work without fear.Records of Group Transfers of Korean Workers, beginning April 1940 (Collected in Truth Investigation into the Chosei Coal Mine Flooding in Japan, Truth Commission on Forced Mobilization during Japan's Colonial Rule, 2015)

Cross-sectional diagram of the Chosei Coal Mine. Created by the Association to Etch the Calamity of the Under Sea Coal Mine Disaster into History. Edited and published in Chōshū Shimbun, March 7, 2024.

Those Who Were Taken

In 1941, when I was eighteen, a Japanese police officer suddenly came to our home (Yeongil County, North Gyeongsang Province — present-day Pohang, South Korea) and took me away. My eomoni (mother) clung to the officer's legs, crying and begging him not to take me. But he dragged me out of the house anyway.Testimony of Kim Gyeonbong. Testimonies and Documents [1]: Father Lies Beneath the Sea, Association to Etch the Calamity of the Under Sea Coal Mine Disaster into History, 2011

At an inn in Busan, a man who said he had been working at the Chosei Coal Mine for three years told us that if we worked hard, we could build a house back home and buy a large rice field.Testimony of Chu Sundeok. Testimonies and Documents [1]: Father Lies Beneath the Sea, Association to Etch the Calamity of the Under Sea Coal Mine Disaster into History, 2011

The moment I entered the dormitory at the Chosei Coal Mine, I found it surrounded by a high wooden fence, about twice the height of a person. No matter how strong you were, there was no way to climb over it. If someone escaped from the dormitory, was unlucky enough to be caught, and was brought back, they were stripped naked. The miners were told, ‘Everyone, watch. There's going to be a beating.’ Then they were beaten with leather straps, not wooden swords—beaten so severely they could have died.Testimony of Shin Seok. Testimonies and Documents [1]: Father Lies Beneath the Sea, Association to Etch the Calamity of the Under Sea Coal Mine Disaster into History, 2011

Why did the Chosei Coal Mine, only a mid-sized operation within the Ube coalfield, employ more Korean workers than any other mine in the region? Behind this was an organized system of mobilization carried out jointly by the government and private industry.

Beginning in 1939, the forcible mobilization of Koreans began under the name of “recruitment” to make up for wartime labor shortages. Some, as Chu Sundeok testified, were brought to Japan with promises such as, “If you work hard, you can build a house back home.” Others, like Kim Gyeonbong, were taken away by force.

According to the Survey on the Conditions of Transferred Korean Laborers, records for the three years from 1939 to 1941 show that the Ministry of Health and Welfare approved the “recruitment” of 1,630 workers for the Chosei Coal Mine, of whom 1,258 were actually brought to the mine.

What awaited the workers gathered in this way was harsh labor under conditions that amounted to confinement. The four dormitories housing Korean workers were surrounded by wooden fences about 3.6 meters high and kept under strict surveillance. All contact with the outside world was cut off, and daily life was limited to going back and forth between the dormitories and the mine tunnels.

In these harsh conditions, workers continued to attempt escape. The labor officers at the time struggled to deal with Korean workers' “escapes,” and records show that by March 1941, more than 150 had fled.

Number of Koreans Brought to the Chosei Coal Mine (Total: 1,258)

• Round 1 – October 12, 1939 249 people
• Round 2 – April 26, 1940 161 people
• Round 3 – May 10, 1940 31 people
• Round 4 – September 21, 1940 72 people
• Round 5 – October 17, 1940 82 people
• Round 6 – October 30, 1940 46 people
• Round 7 – November 30, 1940 49 people
• Round 8 – December 20, 1940 42 people
• Round 9 – March 3, 1941 100 people
• Round 10 – March 26, 1941 160 people
• Round 11 – April 2, 1941 21 people
• Round 12 – April 13, 1941 16 people
• Round 13 – August 24, 1941 109 people
• Round 14 – late October 1941 approx. 24 people
• Date unknown approx. 24 people

A list of names showing the large number of workers brought from the Korean Peninsula (Mining Affairs Division, Records of Group Transfers of Koreans); a plan of the Chosei Coal Mine grounds showing the dormitory that functioned as a de facto detention facility, surrounded by a 3.6-meter fence with a single, constantly guarded exit (created April 1, 1946 by the mine operating company, collection of the Ube City Museum of History and Folklore); and a record noting violence inflicted on Korean workers who attempted to escape (Tokkō Monthly Report, November 1934 issue).

1. At its peak, the Chosei Coal Mine produced approximately 160,000 tons of coal annually, while the major company Ube Industries produced around one million tons. 2. Bringing people under false promises—what was termed gimō (fraudulent inducement)—would have constituted kidnapping even under the laws of the time. 3. Accounts of forcible mobilization also appear in the history of Ube City. 4. The Central Kyōwakai was an organization centered on the Home Ministry and the police, established to control Koreans living in Japan during the war.

The Sealed Pit Entrance

I went down into the mine the day before the flooding accident. Before then, I had not been told anything about water coming into the mine. But there had been a lot of water underground for three or four days, and the two underground supervisors seemed to have some sense that a flooding accident might occur. They seemed to have noticed something. On the day of the accident, I came up from the mine shortly after five in the morning, took a bath, and was resting in the dormitory. Then Supervisor Nakamura came and told me, ‘Put on your work clothes and come to the pit entrance quickly.’ Soon afterward, I learned about the accident.

The pit entrance was already filled with seawater. Police officers and mine staff who had rushed there were arguing and struggling with the families. Before long, they began sealing off the flooded pit entrance with thick wooden boards. … Faced with the desperate situation, the families' cries of ‘Aigo, aigo’ could be heard for a long time.Testimony of Seol Dosul. Association to Etch the Calamity of the Under Sea Coal Mine Disaster into History, Testimonies and Documents [2]: Father Lies at the Bottom of the Sea — The Memorial Completed!, 2014

After the cave-in, two men set out from the pit entrance to rescue those trapped underground: a Korean man whose younger brother had been left behind in the tunnels, and a Japanese man in charge at the site. Despite this, the company operating the Chosei Coal Mine sealed the pit entrance with thick wooden boards, saying that the rising water would reach the machinery outside the entrance.

The families' grief and anger were profound, and a riot broke out the following day. In an effort to bring the situation under control, the company had a nearby temple make memorial tablets and gathered seventeen Buddhist priests to conduct a large funeral service on the beach. Condolence payments for Japanese victims ranged from 300 to 12,000 yen. For Koreans, even 30 yen was considered a relatively good payment.

The accident was reported the following day, but received no further coverage. The company did not even inform the victims' families in Korea of their deaths. Before long, the pit entrance was filled in with earth. The 183 victims remained beneath the dark seabed, left there and in danger of being erased from history.

Those Who Keep the Memory Alive

In 1976, more than three decades after the accident, this tragedy finally began to receive wider attention. Local high school teacher Yamaguchi Takenobu conducted extensive research and published a paper in which he raised the question of whether the disaster “was not simply a mining accident, but also involved Japan's colonial policy and issues of race.”

In 1991, the Association to Etch the Calamity of the Under Sea Coal Mine Disaster into History (hereafter, the Association) was established. Its first initiative was to send “letters to the dead” to the victims' addresses. Of the 118 letters sent, 17 received replies. This led to the formation of an association of bereaved families in Korea.

In 2013, the Association erected a memorial monument. A monument had already been erected locally by people who denied discrimination and forced mobilization. In contrast, the Association's memorial bears the words, “As Japanese, we sincerely apologize to the Koreans and their bereaved families,” and, “We reflect on the history of Japan that gave rise to this tragedy, and pledge to do everything in our power to prevent the emergence of a brutal authority that would once again trample upon another people.” The Association felt strongly that it had accomplished what it had set out to do. Yet it soon found itself setting a new goal.

The turning point came when bereaved families in Korea told them, “We will not stop until we bring the remains back to our homeland. Are the Japanese thinking of giving up?” Co-representative Inoue Yoko recalls that these words marked the point at which the Association broke with what she describes as “a self-satisfied Japanese movement.” The Association began to confront directly the recovery of the remains—something it had previously believed could not be done.

We had thought that recovering the remains was something we could not even begin to undertake. But now we must begin. It will take time. When we think of how deeply the families have suffered, we have to do it. Perhaps only when we have gone that far will this work truly be complete.Yamaguchi Takenobu's final statement at an official gathering, spoken at the memorial gathering following the unveiling of the monument. Association to Etch the Calamity of the Under Sea Coal Mine Disaster into History, Kizamu-kai Newsletter, No. 70 (2018)

Bereaved family members attending the unveiling ceremony of the memorial established by the Association (February 2, 2013).

1. The “Memorial to the Victims of the Disaster,” erected in 1982. 2. Words of Inoue Yoko, current co-coordinator of the Association to Etch the Under Sea Coal Mine Disaster into History.

To Move the Japanese Government to Act

Believing that the Japanese government should take responsibility because the victims had suffered under a state policy, the Association first entered into negotiations with the government. But in negotiations held in 2018, the response was: “The case has not been excluded from investigation, but at present it is not possible.”

To move the stalled Japanese government to act, the Association decided to seek cooperation from the South Korean government. For Japanese people, on the side that had caused the harm, to ask the South Korean government, on the victims' side, for help required, in their words, “the resolve to leap from the stage of Kiyomizu Temple.” Their appeal led to a prompt visit to the site in 2019 by South Korea's Ministry of the Interior and Safety. There, the bereaved families' association, the South Korean government, and the Association confirmed their shared intention to work together toward the recovery and return of the remains. Within Japan, the Association also appealed to members of the Diet across the country. Their efforts led to questions in the Diet and statements in committee sessions. Solidarity with citizens' movements throughout Japan also steadily expanded.

In 2023, the Association finally succeeded in reopening negotiations with the Japanese government. Yet the government's response remained unchanged: “Because the location and depth of the remains are unknown, we ask you to understand that an investigation would be difficult.” Then we will find out for ourselves and create a situation in which the government has no choice but to act. With this in mind, the Association decided to open the pit entrance themselves. And in September 2024, with the support and cooperation of many people, they finally uncovered the pit entrance, whose location had been unknown for many years.

Every time we hold a memorial service, the bereaved families shed tears. Every time. Every year. We know the sorrow and hardship they have endured. I think that is what has sustained us.Inoue Yoko, Co-Representative of the Association. Quoted in Tomoyuki Morimoto, Tokyo Shimbun, October 27, 2024

Members of the Association speaking at a press conference on their negotiations with the government (April 22, 2025); members of the Association, together with ten bereaved family members, in negotiations with the Ministry of the Interior and Safety's division for the repatriation of remains of forced mobilization victims (Jongno District, Seoul, June 3, 2019); and three officials from the Ministry of the Interior and Safety visiting the Chosei Coal Mine site and offering flowers (July 1, 2019).

1. The Ministry of the Interior and Safety of the Republic of Korea includes a division responsible for the return of remains of victims of colonial rule and war.

Breaking Through the Silence

Everyone! The pit entrance is open! This is the pit entrance the bereaved families could never forget and had longed so deeply to see opened. … It is 2.2 meters wide and 1.6 meters high. When a trolley loaded with coal passed through, there was room for only one person to pass. It pains me to think that people were subjected to forced labor in such harsh conditions. How difficult those days must have been.

On behalf of the bereaved families, I offer my heartfelt thanks to everyone who worked to open the pit entrance: co-representatives Inoue and Sasaki, Secretary-General Ueda, and all the members of the Association to Etch the Calamity of the Under Sea Coal Mine Disaster into History; everyone who supported the crowdfunding campaign and made donations; and all those who came from faraway Korea to be here.

For eighty-two long years, the victims have remained beneath the cold sea, far from the mountains and rivers of their homeland and from their families. When I think that they were subjected to grueling forced labor to increase the mine owner's production, and lost their lives with so much left unresolved, my heart aches all the more. When I think of the long months and years they spent, day after day, in a hell of bitterness and suffering—confined, watched by supervisors, and treated not as human beings but as ‘consumables’—I do not know how to express the anguish I feel.

But now the pit entrance is open. May you leave all of this behind and come out. We will come to welcome you. Please forgive, with generous hearts, the many wrongs Japan committed in the past, and let us return home together.

I make this earnest appeal especially to the Japanese government. Do not cling only to humanitarianism in words or to abstract arguments about what is realistic. Take an active part in the work these citizens' groups are doing, and help ensure that the remains, whose recovery the bereaved families so desperately desire, are recovered and returned to their homeland. This is a basic principle of humanity that anyone can understand, and something the Japanese government ought to do. There is a four-character expression, gyeolja haeji (結者解之): ‘The one who tied the knot should untie it.’ In other words, the person who caused a problem should be the one to resolve it.

Once again, I earnestly ask that the remains be recovered and laid peacefully to rest in their homeland. Finally, on behalf of the bereaved families, I would like once again to thank everyone gathered here today at this 'The Pit Entrance Is Open' gathering. Thank you.

Yang Hyeon, Chair of the Association of Bereaved Families of the Chosei Coal Mine Victims, Republic of Korea. Association to Etch the Calamity of the Under Sea Coal Mine Disaster into History, “Kizamu-kai Newsletter No. 94,” 2024.

An excavator advances toward the sealed opening. The main tunnel was discovered at a depth of approximately four meters from the ceiling (September 2024). The uncovered mine entrance, which had been sealed with pine boards (September 30, 2024). After reinforcement work, a public gathering titled “The Mine Entrance Has Been Opened—Bringing Light into 82 Years of Darkness” was held; two piya are visible beyond the site (October 26, 2024). Bereaved families and members of the Association perform chesa (ancestral memorial rites) facing the reopened entrance (October 26, 2024).

Recovery Made Possible by Citizens

I never met my father, and he never had the chance to hold me. But coming here today, I began to feel that perhaps I really could meet him. I have great hopes for the recovery of the remains. I want to scoop up a little water from the pit entrance, because it would be the first time I could touch my father.Tsuneyoshi Katsuhiko (82). ‘We've Opened the Chōsei Coal Mine Entrance!’ Bringing Light into 82 Years of Darkness: Memorial Gathering Held with Bereaved Families from Korea, Major Step Toward the Return of Remains, Chōshū Shimbun, October 31, 2024

After the pit entrance was opened, underwater surveys began, but the work proved extremely difficult. Inside the submerged tunnels, collapsed timbers and corroded iron pipes were tangled together, and once the mud was stirred up, the water quickly became clouded and visibility deteriorated.

At first, the use of an underwater drone was considered. But with so many obstacles in the submerged tunnels, it was judged impractical, and the team turned instead to experienced divers.

Members of the Association, their collaborators, and underwater explorer Isaji Yoshitaka removed the massive iron pipes and timbers blocking their way one by one. In the darkness, they continued to extend a guideline from a reel, gradually opening a route farther into the mine.

Then, in August 2025, their efforts finally bore fruit. Two South Korean divers, Kim Sooeun and Kim Gyeongsoo, entered through the piya and discovered four bodies lying in the darkness of the tunnel. They recovered some of the remains, including a skull.

This overturned the Japanese government's claim that an investigation could not be carried out because “the location of the remains is unknown”—a claim it had used to refuse an investigation.

A body transformed into adipocere, lying inside the tunnel of the Chosei Coal Mine, photographed by the Korean divers (August 26, 2025); two divers transporting a recovered victim's skull while riding in the decompression chamber inside the piya shaft (August 26, 2025); a victim's skull brought up from inside the mine tunnel (August 26, 2025); and underwater explorer Isaji Yoshitaka speaking on the beach with divers Kim Gyeongsoo and Kim Sooeun after the dive survey (August 26, 2025).

What Followed the Opening of the Pit Entrance

• July 30, 2024 Offshore piya feasibility survey: the installation of scaffolding was delayed by a typhoon, and the survey was carried out the following day. For the first time, video footage captured the inside of the piya. Isaji Yoshitaka said there was a possibility of proceeding farther if the structures inside could be removed.
• October 29, 2024 Shore-side piya feasibility survey: the team swam out to the piya. This survey was also delayed by a typhoon. Unfortunately, structures were piled on top of one another inside, making it impossible to reach the bottom. Since both piya were blocked by these structures, the team decided to switch to surveying from the pit entrance.
• October 30, 2024 Pit entrance feasibility survey: the first dive survey was conducted from the pit entrance, which had been opened on September 25. The team explored how far it would be possible to proceed.
• January 31 – February 2, 2025 Dive surveys from the pit entrance: dive surveys were conducted from the pit entrance over three days. During this period, the 83rd anniversary memorial gathering was held, and the dives took place in the presence of bereaved families from Japan and abroad. Unfortunately, the surveys revealed that sections of the tunnels had collapsed.
• March 19–20, 2025 Removal of internal structures inside the piya begins: based on the survey results, the team concluded that the route through the piya might be the better option. A custom-made ladder was installed at the piya, and work began to remove the structures blocking the way.
• April 1–3, 2025 Joint Japan–Korea dive survey from the pit entrance: a joint dive survey was conducted with divers from South Korea. The original plan had been to survey from the piya, but the removal work was not completed in time. The team searched for a route from the pit entrance but was unable to find one, then examined conditions inside the offshore piya.
• June 18–19, 2025 Dive survey from the piya: Isaji advanced farther into the mine from the piya, extending a guideline as he went.
• August 6–8, 2025 Isaji reached the main tunnel from the old tunnel connected to the piya.
• August 25–26, 2025 Discovery of Remains: South Korean divers Kim Sooeun and Kim Gyeongsoo followed the guideline laid by Isaji and confirmed four bodies inside the tunnel. Some of the remains, including a skull and femur, were brought to the surface for the first time in 83 years.
• 2026 The challenge of recovering all the remains: the “Remains Recovery Project 2026” was launched. Divers from around the world were brought together, and using specialized equipment, the team began efforts to recover remains from deeper inside the mine. On February 6, they carried out a second recovery of remains.

Group photo of the divers and the internal diagram of the piya are provided by Isaji Yoshitaka. All other photos are courtesy of the Association.

A Call to Responsibility

Remains are nothing more than bones. But we must bring those bones—the remains of people who died with so much left unresolved—out of the darkness and into the light. We must give them flesh, clothe them, draw their souls back to them, and restore the dignity of the victims.Inoue Yoko, Association to Etch the Calamity of the Under Sea Coal Mine Disaster into History

With the discovery of the remains, the project entered a new phase, moving from “discovery” to “recovering the remains of all the victims.” In 2026, the “Remains Recovery Project 2026” was launched, bringing together divers from around the world to undertake surveys deeper inside the mine. On February 7, 2026, during one of these dives, Hsu Wei (Victor), a diver from Taiwan, died. Hsu was an expert diver with extensive experience in surveys of underwater caves and had undertaken careful preparations for this expedition. The Association suspended the planned search.

As divers, we go into the water believing that whatever happens is our own responsibility. (…) He made the decision to dive based on his own judgment. I believe he made that choice with prideIsaji Yoshitaka, underwater explorer February 2026, at a press conference

“I want to help as many people as possible.” Hsu Wei's family said that this was why he had chosen to take part. They also told the Association, “We want you to continue your work.” After the accident, the Association devoted itself to supporting his family. At their request, it arranged for his cremation and a provisional funeral in Ube, received condolence offerings, and attended his funeral in Taiwan in March.

As for future dive surveys, the Association decided to suspend not only the dives themselves but also discussions about them for one year, in response to a request from the Korean bereaved families' association to observe a year of mourning. During this period, the Association has instead focused on work that had originally been planned for after the dive surveys, including negotiations with the Japanese government.

The Chosei Coal Mine disaster itself occurred in the midst of Japan's wartime national policy. First, increased coal production was promoted as a national project under the National Mobilization Law, and the disaster occurred amid this harsh drive for increased production. Second, many of those who died were from the Korean Peninsula and had been subjected to Japan's colonial rule and forced mobilization by the state. For these two reasons, it is clear that the Japanese government has a responsibility to fulfill.

Yet the government has not undertaken the recovery of the remains as a state project, saying that it cannot provide support for “remains that cannot be seen” and that the victims “were not war dead.” It was citizens and volunteer divers from Japan and abroad who opened the pit entrance, located the remains, and established a path toward their recovery. The costs, too, have been sustained by donations from citizens.

This is not work that should be left indefinitely to private goodwill. Precisely because it is difficult and dangerous, it should be led by the state, which has the expertise, technology, and financial resources to carry it out. The Association has continued to call on the Japanese government to undertake the recovery of the remains as a state project.

At the Japan–South Korea summit in January 2026, the two governments agreed to conduct DNA testing to determine whether the recovered remains could be linked to bereaved families. A path has gradually opened for the remains to return to their homeland. Whether that path can be opened all the way now depends on public support.

Even those who were still in their mothers' wombs at the time of the disaster are now in their eighties. The bereaved families do not have much time left. To respond to the victims who have waited beneath the cold seabed for more than eighty years and to the hopes of their families—and to build a future in which every human life is valued above all else—let us raise our voices together and widen this circle of support.

Negotiation History with the Japanese Government

• February 8 and December 3, 2018 Association–government negotiations: The Chosei Coal Mine case “has not been excluded from investigation, but at present it is not possible.”
• April 7, 2023 Special Committee on Official Development Assistance and Okinawa and Northern Territories Affairs. Foreign Minister Hayashi Yoshimasa: “If circumstances allow, I hope we can consider a visit to the site.”
• December 1, 2023 House of Councillors. Minister of State Matsuno: “Because the location and depth of the remains are not clear, we consider it difficult at this time to carry out the ‘excavation of remains’ you have raised.”
• September 25, 2024 The pit entrance is opened.
• April 7, 2025 House of Councillors Budget Committee. Prime Minister Ishiba, on the current state of the survey at the Chosei Coal Mine: “I understand there are considerable safety concerns.” “The government cannot simply say it is ‘self-responsibility’ while knowing the danger.” “If seeing the site firsthand would allow for a more accurate grasp of the situation, or if it would gain the understanding of those involved, I do not think we should hesitate to visit the site.” “I am well aware of the importance of the remains being discovered through safe work and returned to their families. We would like to consider, within the government, what kind of support the state should provide.”
• April 22, 2025 Association–government negotiations. Ministry of Health, Labour and Welfare: “After hearing more details of future plans, we would like to consider our response while gathering expert knowledge.” “Budgetary support may also be possible.”
• August 19, 2025 Association–government negotiations. Ministry of Health, Labour and Welfare, on the expert knowledge it had said in April it would gather: “We have found no new findings.”
• October 21, 2025 The Takaichi administration is inaugurated.
• October 21, 2025 Association–government negotiations. After the Association provided 31 DNA samples from bereaved families, the National Police Agency said: “It has not even been decided whether the police will be the ones to conduct the testing; the matter may be left entirely to the South Korean government.” The Ministry of Health, Labour and Welfare said that, regarding safety confirmation, it had not yet consulted experts on a boring survey to check for cracks near the remains-recovery site, or on constructing a vertical shaft to introduce an underwater drone from the shore and offshore sides of the site, both of which had been left pending, and that “we cannot support work at the piya.”
• After the discovery of the remains A senior National Police Agency official said that if the government did not carry out DNA testing of the remains for return to families by February 2026, the Association planned to have the testing done independently. The official had suggested that privately conducted testing, since it damages the remains, could constitute the crime of damaging a corpse; however, Professor Maeda Akira, professor emeritus at Tokyo Zokei University (criminal law and human rights), published an opinion stating that it “does not constitute the crime of damaging a corpse.”
• January 13, 2026 Japan–South Korea summit. The Japanese government stated that it would commission DNA testing from specialist agencies and would also consider entrusting the work to South Korean agencies, aiming to return the remains to bereaved families where blood relationships are identified.
• January 30, 2026 Officials from the Ministry of Health, Labour and Welfare and experts make their first visit to the site.
• February 7, 2026 Hsu Wei (Victor), a diver from Taiwan, dies during a dive survey at the Chosei Coal Mine.
• April 30, 2026 Association–government negotiations. In negotiations with the Ministry of Foreign Affairs and the National Police Agency, the Association called for the prompt implementation of DNA testing, which had still not begun despite repeated requests.
• June 30, 2026 Association–government negotiations. Ministry of Health, Labour and Welfare: “Because safety cannot be confirmed, we are not considering further recovery [of remains] at this time.”