She was part of Dentsu's online advertising division, which recently had its staff numbers cut from 14 to six, according to the Japan Times. Takahashi had worked more than 100 hours of overtime every month since joining the company in April last year, Japanese media reported.
In the weeks leading up to her death, she reportedly began writing messages on Twitter in which she complained of being forced to work extremely long hours. "It's 4 o'clock. My body is trembling ... I just can't do this. I'm gonna die. I'm so tired," one message read.
Tadashi Ishii, the president of Dentsu, said in a statement it was "extremely regrettable" the company had failed to "prevent overwork by a new recruit".
"In order to take full responsibility, I would like to resign as president at a board meeting in January," he added.
Shinzo Abe, the Japanese Prime Minister, is campaigning for sweeping reforms of employment laws, which could include tighter regulation of overtime. It is not the first time a Dentsu employee has killed themselves due to overwork. In 2000, Japan's highest court ruled that a 24-year-old employee took his life due to suffering "horrendous working conditions".
It is unclear how many victims of "karoshi" there are each year in Japan, but estimates put the figure in the hundreds, or even the thousands. Overall, in 2014, there were 25,000 suicides in Japan.
The rigorous working culture - where shifts of 12 hours or longer are often considered the norm - is understood to have begun in the 1970s, when wages were low. The culture continued through the 1980s boom and is often credited with pushing Japan to become the world's third-largest economy.
But it has also been harshly criticised for leaving workers miserable, exhausted, and in some cases suicidal.
