Personally, what most shocked me is how accepted and common this is.
To the point that when I friend came to study to Spain she asked me: "Why is no one sleeping in the library?"
On the other side, I believe it's also dangerous. I visited Malaysia with my gf, and she would fall asleep in every train and taxi because it's just what they do.
I also commonly see people taking naps during lunchtime in Starbucks. Someone will come in, grab a coffee, take a nap for 30 min, drink the coffee and go back to work. There's nothing wrong with that! (other than I want the table :P)
Unfortunately the corporate culture is not where it should be. There are some companies that want to be like western startups where taking a nap on the office sofa wouldn't raise an eyebrow but those are very rare. In most Japanese companies it would be totally unacceptable to sleep in the office.
They're cultures that you can see "see people at McDonalds early in the morning after a night out" all the time, without having to go there directly from working late...
It is great that you can safely take a nap in a public space without fear of being robbed or worse (as one would have to fear outside Japan), without having police called on you, and with general public acceptance of such action.
Nobody will think you're a bum or a mad or look at you funny. Try that somewhere else and let's see what happens!
Japanese corporate culture is terrible and that is sad. I don't have an answer to that.
Broken according to which cultural paradigms? Just because we have different ideas in the west does not make them better.
In all the coffeeshops in Austin, Texas at least, I've seen baristas wake up customers who are napping. But I understand why they do that: there are many homeless people around and if anyone could just take naps...