KOCHI--Setsuko Shimomoto will soon travel to a far-flung Pacific island where her late father fell victim to a tragedy 70 years ago that he never spoke about with her. 

Tobei Oguro was a crew member aboard one of the ill-fated tuna fishing boats that was exposed to a U.S. hydrogen bomb test over the Bikini Atoll in the Marshall Islands after World War II on March 1, 1954.

Oguro was one of many crew members exposed to the radiation fallout. He died of bile duct cancer 22 years ago at the age of 78.

Shimomoto, 73, who lives in Kochi and is seeking relief from the government, will participate in a ceremony on March 1 in Majuro, the capital of the Marshall Islands, to mark the 70th anniversary and honor the victims. 

“It will be my first trip abroad in my life,” said Shimomoto.

“I decided that if the bereaved family could go, there would be something to be able to pass on,” she said at a meeting held in Kochi on Feb. 16.

The hydrogen bomb test conducted by the United States in the Marshall Islands exposed the crews of many Japanese fishing boats and cargo ships to radioactive fallout known as “ashes of death.”

Between 1946 and 1958, when the United States and the Soviet Union (now Russia) competed to develop nuclear weapons, the United States conducted nuclear tests in the Marshall Islands 67 times.

Radiation was detected in the hulls of the exposed ships, and it was said to be the “third nuclear disaster” following the Hiroshima and Nagasaki atomic bombings.

But the Japanese government discontinued the follow-up investigation.

In 1954, a total of 992 fishing boats in Japanese ports were forced to discard tuna catches when radiation was detected in the ships. 

The series of damages, known as the “Bikini Incident,” was the genesis of the campaign to ban atomic and hydrogen bomb testing. 

The incident, which became a thorn in the side of Japan-U.S. relations, was brought to a close in January 1955 with the signing of a U.S.-Japan agreement. 

The settlement allowed the United States to pay $2 million to Japan in compensation without conducting a follow-up investigation of most of the crew members.

For Shimomoto, the tragedy finally hit close to home in 2004, two years after her father’s death.

She attended an exhibition on the Bikini Incident in Kochi and saw a poster calling for former crew members and their bereaved families to contact an organization.

“My father was a man of few words and he never said a word about the Bikini Incident,” she recalled.

But she remembered her mother telling her that he had attended a meeting of people who had been exposed to radiation from the testing.

Shimomoto called the contact number on the poster.

She was connected with Masatoshi Yamashita, 79, a former high school teacher in Sukumo, Kochi Prefecture.

Yamashita is an adviser to a peace education group. Since 1985, Yamashita along with high school students have been conducting interviews with former fishermen and had met Shimomoto’s father.

Yamashita told Shimomoto about her father's experiences, which she had never been told about.

She learned that her father boarded a tuna fishing boat based in Muroto in the prefecture at the age of 30.

He was exposed to the “ashes of death” during a three-week voyage in the waters around Bikini.

Her father had left the ship at the age of 36 due to illness and had undergone surgery for stomach cancer in his 50s, she learned.

She said she felt as if her fragmented memories of her father were connected by a single stroke.

In 2014, 60 years after the incident, Yamashita talked to former crew members and their bereaved family members, and called for filing a compensation lawsuit against the state. 

The suit was based on official documents he had obtained through a request to the government for information on the fishing boats and the radiation doses of the crew members. 

Two years later, 45 plaintiffs filed suit in Kochi District Court. Shimomoto joined the lawsuit. 

In 2018, the district court ruled that all but one of the former sailors had been exposed to radiation, but the plaintiffs lost the case. The same was true of the Takamatsu High Court decision the following year. 

From 2020 to 2022, 19 people filed an administrative lawsuit with the Kochi District Court. Shimomoto is the leader of the plaintiffs. 

One of the main focuses of the lawsuit is how to prove a causal relationship between radiation exposure and health damage.

“It is unreasonable for the victims to have to prove a causal relationship,” Shimamoto said.

Through the court battles, Shimomoto learned that there are many “global hibakusha” around the world who live with health concerns because their residential areas were contaminated by nuclear tests or they were exposed to radiation after being present as soldiers. 

In preparation for her visit to the Marshall Islands, she has also learned about the damage inflicted on the Marshallese people by the nuclear testing.

Even though they do not speak the same language directly, Shimomoto believes that people can be connected by their common desire that “the nuclear damage must not be repeated.”