I may be reinforcing stereotypes, but I am sure many Korean minimart owners in the US are working 80 hour weeks. Yes they are driving Mercedes and BMWs, but I do not envy them.
There's a good amount of truth to that. My girlfriend is Korean-American and lived in the ROK until she was in her 40s. Her early years here were tough for many reasons,including limited English. She averaged 80 hour work weeks during those days and even today,when her situation is far more settled she averages 50-55 hours a week.
Neither Koreans nor Japanese are afraid of hard work or long hours.