With her mobile phone in hand as if waiting for her next assignment, a 31-year-old political reporter with broadcaster NHK died of heart failure in her sleep in July 2013 after clocking nearly 160 hours of overtime the month before.

Two years later, on Christmas Day, a rookie at advertising giant Dentsu leapt to her death after being subjected to a gruelling schedule and harassment at her workplace.

These cases of lives snuffed out way too soon, which made headlines last week, are the tip of the iceberg and have renewed scrutiny of Japan's notorious overtime culture.

NHK, which belatedly came forward with the news of Ms Miwa Sado's death last Wednesday with the go-ahead of her parents, promised to undergo serious soul-searching and implement workplace reforms.

Dentsu, meanwhile, was slapped with a token 500,000 yen ($6,060) fine by a Tokyo court last Friday over labour violations that led to Ms Matsuri Takahashi's suicide at 24.

Her widely reported case has become a cause celebre against excessive overwork, sparking a deep rethink in Japan over its labour laws

Yet, this was not the first time Dentsu - which until Ms Takahashi's death had as a guideline: "Once you start, don't quit - even if it kills you" - has made the news for the wrong reasons. In 1991, Dentsu employee, Mr Ishiro Oshima, also 24, killed himself in what was the first case to be recognised by courts as death by overwork or "karoshi".

The statistics nationwide are quite startling. Japan's second annual karoshi White Paper, released last Friday, said there were 191 work-related deaths and attempted suicides in the fiscal year ending March 2017. This was two more than the previous year. In the same fiscal year, 498 cases of mental illness, such as depression, were deemed work-related.

And from January 2010 to March 2015, 368 suicides - 352 men and 16 women - were deemed as karoshi.

The pernicious trend of excessive overwork first took root in the post-war boom years as workers tried to maximise their earnings, and then remained after the economy slowed as employees did not want to be seen as slacking off amid concerns over their job security.

Japan has reacted to Ms Takahashi's case by drafting new laws, including overtime caps of up to 100 hours a month and 720 hours a year.

To work overtime for 100 hours in a standard month of 20 workdays would mean clocking an average of five hours per day - on top of the standard eight-hour workday.

The debate in Parliament over these new laws was expected in the session starting Sept 28, but has been put off after the Lower House was dissolved for a snap election on Oct 22. Japan has set April 2019 as the target to roll out the new caps, which has drawn flak.

First, critics have argued that the dangerously high cap seems to endorse a standard on the number of hours to be logged before a worker's health is threatened.

Second, the laws would initially not apply to high-demand professions like doctors and lorry drivers.

But the transport and postal industries contributed to the largest numbers of karoshi incidents in the last fiscal year, with 41 deaths.

The medical profession, too, made the news after an Osaka national hospital was found last month to permit up to 300 hours of overtime per month under a labour management pact.

Earlier this year, the death of Ms Aya Kimoto, 37, a female trainee doctor at a Niigata hospital, in January last year was deemed as karoshi as she clocked 251 hours in overtime the month before she died.

Further, amid moribund wage growth and with salaries still boosted by the number of overtime hours, there are concerns that fewer hours clocked at work could mean lower take-home salaries.

The government had, in May, also for the first time released a nationwide list of over 300 companies that have violated labour laws in a name-and-shame tactic.

This followed the Premium Fridays scheme that started in February to encourage companies to let their workers knock off at 3pm on the last Friday of each month.

A Ministry of Economy, Trade and Industry (Meti) spokesman told The Sunday Times that the goal was to "convey the philosophy" of work-life balance, even if results were not immediately optimal.

Meti Minister Hiroshige Seko last month, in noting the operational difficulties faced by some companies in implementing the scheme as they need to meet month-end deadlines, said he was considering shifting the scheme to the start of the month.

Even so, these new measures have come too little, too late, for many. This March, an unnamed 23-year-old construction supervisor, fresh out of university and involved in building the new 2020 Olympic Stadium, killed himself after 211 hours of overtime in a month.

"My physical and mental state have been stretched to their limits, and there is no other way out," he wrote in a suicide note.

His lawyer said that the overwork had led to "depression, a decline in self-confidence and a pessimistic point of view about life".