There is always a peer pressure to stay behind at work. If one leaves early - they are 'slacking'. If they work late then it looks like they are doing a good job - or they 'feel' that they are doing a good job. The boss doesn't leave early because they feel that they cant leave their staff behind. Subordinates dont leave early because they feel they cant knock off before their boss - evil circle.
If you dont like this style of work, make sure you land yourself a results oriented job when looking for
work in japan.