In the space of eight months after landing a much coveted position at advertising giant Dentsu in April 2015, Matsuri Takahashi transformed from being a personable, diligent and well-liked young woman to a physical and mental wreck who was getting just 10 hours of sleep a week and was being bullied by her superiors.

Her social media messages reveal the despair that 24-year-old Takahashi had been feeling as the pressure built. The 105 hours of overtime she was working each month – on top of her regular eight-hour, five-day-a-week routine – left her exhausted and depressed, while the criticism of her immediate boss made her feel worthless, she wrote.

Something, inevitably, had to give.

On December 25, 2015, Takahashi jumped from the top of the company dormitory where she lived.

A little over eight months later, the Mita Labour Standards Inspection Office ruled that her death had been caused by overwork, a phenomenon known here as “karoshi”. Most worryingly, in a society where workers are expected to put their company and work colleagues above everything else, it is far from a rarity.

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The Japanese government released its first ever investigation into the karoshi crisis in early October, revealing that staff at 12 per cent of corporations put in more than 100 hours of overtime every month.

Employees of a further 23 per cent of the nation’s companies were only slightly better off, working 80 hours of overtime each month.

And the true figures may be even worse, as only 1,743 of the 10,000 companies across the nation invited to take part in the inquiry did so.

In the 2015 fiscal year, which ended on March 31, the Ministry of Health, Labour and Welfare recognised 93 suicides and attempted suicides as having been caused by overwork, enabling dependents to claim compensation. That figure jars with police statistics, however, which indicate problems related to work were to blame in 2,159 suicides that year.

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The ministry’s figures are also overshadowed by the number of legal cases filed by relatives of victims of karoshi. In the year to April 2015, 1,456 cases were filed with authorities. In comparison, in the four years between 2004 and 2008, 1,576 cases were filed.

“We can see many reasons why the problem is becoming more acute, but the single largest reason is the excessive sense of competition in society here,” said Hiroshi Kawahito, president of the Tokyo-based Kawahito Law Office and head of the National Defence Counsel for Victims of Karoshi.

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“In the years since Japan’s economic bubble burst, in the early 1990s, the nation’s economy has been stagnant and companies have had to reduce their costs,” he said. “For many, the easiest way to do this is by cutting their numbers of full-time, salaried employees and replacing them with workers on temporary contracts.”

As a result, salaried workers feel pressure to work harder and put in more hours just to safeguard their positions.

In the past decade, long hours, unpaid overtime – known euphemistically as “service overtime” – and shorter holidays have become the norm.

Kawahito says that part of the problem is that Japan’s labour laws “have no teeth”. While the laws are set, companies can get around them by signing agreements with workers and unions, which are primarily interested in keeping their members in employment.

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The government has, at least, recognised there is a problem and in 2014 enacted legislation that requires labour authorities to monitor companies and look into cases of death or ill-health caused by excessive workloads. In 2015, the government investigated 2,362 complaints and issued warnings or punishments in 60 per cent of those cases.

The concern is that with a shrinking number of youngsters entering the workplace and greater pressure on companies to cut costs and raise productivity, cases of karoshi will inevitably rise.

At least the death of Matsuri Takahashi has brought the issue into the spotlight, with even the conservative and pro-business Yomiuri newspaper this week running an editorial thundering that there seemed to be “no end to heart-rending cases of suicide induced by overwork” and that the “public and private sectors must speed up efforts to eradicate such deaths”.

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Addressing a press conference after the labour office’s ruling and sitting behind a picture of her daughter, Yukimi Takahashi said: “No job can be more important than life. I strongly hope that the government will tell this to businesses as soon as possible.

“My daughter will never come back to me.”

Despite Yukimi Takahashi’s plea and all the worrying statistics that surround what are essentially deaths being caused by corporate culture, not everyone is sympathetic to those who cannot bear the strain any longer.

On the same day that the government released its white paper on karoshi, Hideo Hasegawa, a professor at Tokyo’s Musashino University, posted a message on an online news site stating: “It is pathetic for someone to die just from working more than 100 hours a month.”

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The comment quickly attracted a storm of criticism and the university issued a statement, saying it “sincerely apologises for his comment that made people feel displeased”.

Hasegawa also expressed regret for his post, although perhaps not for the sentiment behind it. The professor’s apology said he was “sorry my selection of words was rude”.

Julian Ryall is a journalist based in Tokyo