Not paying overtime is the biggest "sin" a potential employer can commit to get labeled as an abusive "black company" to be avoided by college students entering the job market, according to a survey of young job hunters.

Over 60 percent of 1,650 university and graduate school students polled in January by Tokyo-based recruitment consulting firm Disco Inc. said they wouldn't consider applying to firms labeled or rumored to be "black."

Asked what typifies a so-called black company, respondents cited extended overtime, low wages and various forms of harassment, and a high turnover rate among young workers.