The situation detailed in the government's first-ever white paper on karoshi, or death from overwork — mandated by the 2014 law aimed at promoting efforts to prevent such deaths — points to the need to place effective caps on the working hours of the nation's company workers. As part of his administration's much-touted "work-style reforms," Prime Minister Shinzo Abe reportedly seeks to introduce a legal ceiling on the overtime hours that a worker can clock a month, but there are resistance to tight uniform caps from business circles, particularly among industries that suffer from manpower shortages.

The law, introduced two years ago as a response to the social problem that has been serious since the late 1980s, makes it the state's responsibility to take steps to prevent death from overwork but does not provide for regulations or penalties to achieve that. It calls on the government to study the situation of heavy workloads that impair the health of company workers and lead them to take their own life.

According to the annual report released last week, 23 percent of 1,743 companies surveyed said they have employees who have worked more than 80 hours of overtime a month — a criteria beyond which a worker's death can be linked to overwork — including 12 percent that replied that some of their employees clocked more than 100 hours of overtime in a single month. The ratio shoots up to 44 percent among companies in the information and communications business, 40 percent in the research and technology service sectors and 38 percent in trucking and postal businesses.