Fate of media worker Miwa Sado, 31, piles pressure on authorities to address large number of deaths linked to labour practices
Miwa Sado, who worked at the broadcasters headquarters in Tokyo, logged 159 hours of overtime and took only two days off in the month leading up to her death from heart failure in July 2013.
A labour standards office in Tokyo later attributed her death to karoshi (death from overwork) but her case was only made public by her former employer this week.
Sados death is expected to increase pressure on Japanese authorities to address the large number of deaths attributed to the punishingly long hours expected of many employees.
The announcement comes a year after a similar ruling over the death of a young employee at Dentsu advertising agency prompted a national debate over Japans attitude to work-life balance and calls to limit overtime.
Matsuri Takahashi was 24 when she killed herself in April 2015. Labour standards officials ruled that her death had been caused by stress brought on by long working hours. Takahashi had been working more than a 100 hours overtime in the months before her death.
Weeks before she died on Christmas Day 2015, she posted on social media: I want to die. Another message read: Im physically and mentally shattered.
Her case triggered a national debate about Japans work practices and forced the prime minister, Shinz Abe, to address a workplace culture that often forces employees to put in long hours to demonstrate their dedication, even if there is little evidence that it improves productivity.
The government proposes to cap monthly overtime at 100 hours and introduce penalties for companies that allow their employees to exceed the limit measures that critics say still put workers at risk.
In its first white paper on karoshi last year, the government said one in five employees were at risk of death from overwork.
More than 2,000 Japanese killed themselves due to work-related stress in the year to March 2016, according to the government, while dozens of other victims died from heart attacks, strokes and other conditions brought on by spending too much time at work.
According to the white paper, 22.7% of companies polled between December 2015 and January 2016 said some of their employees logged more than 80 hours of overtime each month the level at which working hours start to pose a serious risk to health.
Research shows that Japanese employees work significantly longer hours than their counterparts in the US, Britain and other developed countries. Japans employees used, on average, only 8.8 days of their annual leave in 2015, less than half their allowance, according to the health ministry. That compares with 100% in Hong Kong and 78% in Singapore.
Sado, a political reporter, covered the Tokyo metropolitan assembly elections and national upper house elections in June and July 2013. She died three days after the upper house elections.
Masahiko Yamauchi, a senior official in NHKs news department, conceded that Sados death reflected a problem for our organisation as a whole, including the labour system and how elections are covered.
Yamauchi said NHK had waited three years to make Sados death public out of respect for her family, according to Kyodo news.
In a statement issued through NHK, Sados parents said: Even today, four years on, we cannot accept our daughters death as a reality. We hope that the sorrow of a bereaved family will not be wasted.
In the UK the Samaritans can be contacted on 116 123. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is on 13 11 14. Other international suicide helplines can be found at www.befrienders.org.