In Japan, a million people have shut themselves in their rooms

Working conditions vary hugely from company to company. On a spectrum from "black companies" -as they're called here- to "modern companies" with strict enforcement of work/life balance in terms of office hours and (lack of) overtime. Also, in my experience there's often a lot of variance within the same office too. Usually between those who have learned to set their own boundaries and those who haven't.

If anything, conditions are often the _opposite_ of rigid. Overtime is far more strictly regulated in Japan than in the US, for example. As such, blatantly over-exerting employees is nowhere near as common here as people overseas seem to assume. Because that kind of thing can land a company in a lot of trouble.

It's usually rather the un-rigid aspects that lead to stressful working conditions, as far as I can judge. People here generally strongly value being considerate of those around them, especially in terms of not being a burden to others, and one way this manifests itself is by a drive to meet implicit expectations of coworkers -- real or imagined. Over-promising and over-committing is a common mistake anywhere, but its an even easier trap to fall into in a country like this where expectations aren't rigidly outlined at all.

> The extremely rigid gender roles expected by society are another.

Well, yes, I concede that there is (still) a far larger gender-based bias in societal expectations than in many Western countries. However, wouldn't you say that in most aspects women are the side that draw the shorter sticks here? And yet, about 3 in 4 hikikomori are boys/men, so I'm not sure what kind of conclusion you'd want to draw from that...

And as for me being a "gaijin"? That's not even relevant, because my observations are based not on how people interact with me, but rather how my Japanese coworkers tend to communicate with each other on the numerous (almost exclusively open plan) work floors I have been part of for many years.