Miwa Sado, a political journalist for NHK, Japan's national public broadcasting organisation, suffered a heart failure in July 2013, though her employer made the case public this week, the Japan Times reports.
31-year-old Sado died just three days after reporting on a local election in the House of Councillors.
Masahiko Yamauchi, a senior official at the broadcaster, said Sado's death was a "problem for our organisation as a whole, including the labour system and how elections are covered".
"Even today, four years after, we cannot accept our daughter's death as a reality," her parents said in a comment released by NHK.
"We hope that the sorrow of the bereaved family will never be wasted." it added.
However, the report further mentioned that the Japanese Prime Minister Shinzo Abe's administration has been seeking to improve working conditions in the country, following the suicide of a new recruit at advertising giant Dentsu Inc. in 2015 due to excessive working hours.
According to labour standards inspectors's conclusion, drawn in September 2016, sparked debate on the harsh working conditions in the country led to the suicide of 24-year-old Dentsu employee Matsuri Takahashi in April 2015.
Dentsu is also on trial for labour practice violations, with a ruling set to be handed down by a Tokyo court on October 6.
According to a national survey, one-fifth of the country's workforce are at risk of karoshi - death from overwork - since they clock more than 80 hours extra work time each month. (ANI)