Weekly Book Discoveries, issue 455, 22 October 2026. Reviewed by Hiroko Shimizu.

The Dark Sea: Tears of Forced Labourers (黒い海――強制徴用者の涙), by Moon Young-sook, illustrated by Kim Se-hyeon and translated into Japanese by Sachiko Kitamura. Published by Kage Shobō.

I picked up this book because I wanted to learn more about the Chosei coal mine. I first heard about it in 2024. Only then did I discover that its workings lay beneath the seabed. Until that point, I had not even known that such mines existed. I had heard about coal mines in Kyushu and Hokkaido, but never about mining under the sea.

On the morning of 3 February 1942, the Chosei mine flooded in workings about a kilometre offshore — a disaster referred to as a “water emergency”. It killed 183 miners. Of these, 136, more than 70 per cent, had been brought from the Korean Peninsula, then under Japanese colonial rule. For decades, the dark, cold sea remained the victims’ grave.

In 2024, I saw a report that the mine entrance had been located and reopened so that work could begin to recover their remains. Even then, I struggled to imagine a coal mine beneath the seabed. I knew the conditions must have been brutal, but I had no real sense of the work and daily life people were forced to endure there. Then, in August 2025, news came that victims’ remains had been found. Their reappearance after 83 years left me deeply shaken.

The book is based on the life of Kim Gyeong-bong, a survivor of the Chosei mine flooding. In her afterword, the author, Moon Young-sook, writes:

“I read a newspaper article about the elderly Kim Gyeong-bong, who had survived the flooding of the Chosei coal mine in Japan. That was the first time I learned that a coal mine could lie beneath the sea. Some time later, driven by a sense of duty, I went to visit him. Holding back his anger, he told me how he had been forcibly taken to Japan for labour and had barely escaped death. […] Many people, like Kang-jae, the protagonist of this story, were deceived by plausible lies and ended up in Japan. Most of what happens to Kang-jae in the book comes from Kim Gyeong-bong’s own experiences at Chosei.”

Kang-jae’s home is in Gyeongsang Province, in Korea, which Japan had colonised. Japan’s war reached even there. Coal was vital to military production and industry. Under colonial rule, Koreans were forcibly mobilised for mine work through successive systems of recruitment, government-arranged placement and labour conscription. Coal mining was directly bound up with colonialism and the war effort.

The story begins when Kang-jae and his friend Cheon-seok are taken from their Korean hometown to Japan, to the Chosei coal mine. There, a Japanese man named Kobayashi, whip in hand, first teaches them the oath of imperial subjects. Each is assigned a number. Reading about the life and work forced on Kang-jae made me tense up in horror more than once. Staying there would mean waiting for death.

Kang-jae and Cheon-seok try to escape, but fail and are separated. Kobayashi stops short of killing Kang-jae only because he cannot afford to lose a worker. Then the mine floods. Kang-jae barely escapes with his life and sets out to find his friend. With each page, I grew more eager to know what would happen next. He finds Cheon-seok, physically and psychologically broken, and, looking after him, boards a ship bound for home. Home is close. They can go home.

The book vividly conveys how Kang-jae was taken to the mine, the work he was forced to do, the treatment he received and everything he endured. A place I had struggled to imagine became tangible and real.

The material at the end is also valuable: afterwords by the author and translator, and two essays. These are “Together with Korean Victims and Their Families”, by Yoko Inoue, who heads the Association for Commemorating the Chosei Coal Mine Flooding Disaster, and “To Prevent the Repetition of War, Colonial Rule and Forced Labour”, by the journalist Yujin Fuse.

I wanted the story to reach not only adults like me, who want to learn about Chosei, but also Japanese primary and lower-secondary school pupils. As someone who knows little about children’s literature, I may be presumptuous in saying so. Yet I believe this is an outstanding story, one that exposes the horrors of war in ways that history books and documentaries cannot.

In her afterword, the author explains why she wrote the book:

“Until the Pacific War ended, Japan forcibly took young Korean men not only to Japan itself, but also to distant Pacific islands — Palau, Saipan and unnamed islands — where they were driven into the line of fire as human shields. When the war ended, the Japanese withdrew and abandoned them. Taken by force and left behind, these young men lived like beasts and died in the jungle. Through this story, I wanted to comfort the souls of tens of thousands of conscripted labourers who had lost their homeland, been taken away against their will and met miserable deaths. I also wanted to go further and expose the horrors of war. I wanted to offer some solace to the many souls who could not return home and wandered in unfamiliar lands.”

We adults should first take these words to heart. But they also raise a question about education in Japan. To understand this story, schoolchildren need to know the realities of Japanese colonial rule and the war. Are these subjects taught in Japanese schools today? Without knowing the historical facts of what Japan did, and without understanding its role as a perpetrator, will children find this story merely an abstraction, disconnected from reality? That is what worries me.

Finally, I recommend the website of the Association for Commemorating the Chosei Coal Mine Flooding Disaster, which I also consulted. Visit the association’s website