I have worked with Japanese colleagues and they have told me that the work pressure is extreme in Japan. You are not supposed to make a single mistake, no matter how small it is. You should always deliver your output on time, and it should be of the required quality. It is almost impossible for outsiders to adjust with the Japanese work culture.
However, I heard that the Japanese are literally persuaded to go on vacation and stay at work. So the work does not bring him stress? Strange country for me, but I would love to lived there 1-2 years.