Work goes on from 8am - 9pm, after which many are expected to go out and socialize with their colleagues (karaoke etc) and get drunk until 3am. Rinse and repeat, most days of the week. It wasn't at all unusual to see rows of salarymen asleep on the subway every morning.
Japan's most popular drink is a brand of canned coffee which is on sale everywhere and in the vending machines that line the streets. Coca Cola's brand of this coffee accounts for an outsize proportion of their global profits (something like 12%, only sold in Japan).
All of this seems to be totally okay and accepted despite the obvious impact on productivity of regularly going for long periods without sleep. This is the offices of Dentsu, Japan's largest media agency, at night: https://m.youtube.com/watch?v=EWX6--sQtsA