The boss of Japan's largest advertising agency will step down following the suicide of a young worker who allegedly worked hundreds of hours in overtime.

Matsuri Takahashi, a worker at Dentsu, took her own life in December last year in what the Japanese government has determined was due to "karoshi" also known as "death by overwork", the UK Telegraph reports.

The 24-year-old left a note for her mother which reportedly begged the question: "Why do things have to be so hard?"

In a statement announcing his resignation, Dentsu president Tadashi Ishii said it was "extremely regrettable" the company 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 said.

In light of her death, Dentsu and one of its executives could face prosecution amid claims the company forced Ms Takahashi to work longer hours which violated Japan's labour laws.

In the lead up to her death, the young worker reported wrote of her anguish on social media at being bullied in the workplace to work longer hours.

"It's 4 o'clock. My body is trembling… I just can't do this. I'm gonna die. I'm so tired," the Telegraph quotes one of the messages as saying.

Tragically, Ms Takahashi is not the first Japanese worker to take their own life due to being overworked. In 2000, Japan's high court determined that another 24-year-old worker had hanged himself because of "horrendous working conditions".

According to a white paper released by the Japanese government, 12 percent of Japanese workers put in more than 100 hours of overtime every month. The figure is based on the response of almost 20,000 workers.

Dentsu president Tadashi Ishii said it was "extremely regrettable" the company failed to prevent overwork by a new recruit. (AAP)