According to The Daily Mail, the auto company was found liable in the worker's death because he killed himself after being chronically overworked. According to the parents' suit, the employee was ridiculed publicly by his managers for, among other accusations taking "needless" overtime.
Mazda paid the young man's parents a separate condolence settlement in 2009. Work-related suicide is becoming a real problem in Japan, where the culture favors a workaholic mentality. In addition, many chronic overworkers suffer stress-related heart attacks and strokes.
These sorts of deaths have become common enough that the Japanese have coined a term, "karoshi," which means "exhaustion death" to describe the phenomenon. Courts have ruled that the employer can be held liable in karoshi cases, as has apparently happened with Mazda.
[Source: The Daily Mail]