I live and work in Japan since 2011. The most part of this time in larger companies. Afaik Dentsu takes or took huge pride in being an elitist salaryman operation. People joining them couldn't be totally unaware of this. Keyence is another place with a similar reputation. Although you'll find more places like this, it is not that common. I am pretty sure every country has companies like this.
Further, Japanese people work long hours. Some will due to peer pressure. Some will cause they have nobody waiting at home. In some workplaces your colleagues are like friends. So, they socialize a lot during work hours. I think there is no single reason why Japanese people work longer hours than Europeans for example.
I am convinced however, that on the average a Japanese employee takes a huge amount of pride from doing a good job. The point: How to judge if a job was executed well or not? I experience this not to be so easy mostly due to the Japanese style of communication, which leaves a lot of space for ambiguity. Maybe long work hours stem from this.