Night train is very popular around the world, and it's a hit with tourists because they can save extra day on hotel expense and travelling time. It's a kind of travelling hack.
Japan Sunrise Night Train is extremely popular and tourist need to book them several weeks in advance to get a ticket [1]. You can use Japan Rail Pass card for the nobi-nobi economy seats but need to pay extra for the private compartments.
I think it depends how you look at it, but night trains in Japan are actually not that popular -- so much so they had to reduce routes so the Sunrise Seto became the only surviving night train (as pointed out in your linked article), which why it's hard to book.
I actually wanted to book it from Osaka to Tokyo, but there were a number of hoops to jump through to book it from abroad with a JR Rail Pass that hadn't yet been exchanged, that I ended up just book another hotel night and then hopped on an morning Shinkansen to Tokyo.
Barely anyone takes the Sunrise Seto. I managed to easily book it while I was there. I really want to take it again when I am back, 100% quintessential Japanese bliss. I hope they never get rid of it.
As an American sleeper train enthusiast, my recs are:
- If you find yourself in Germany, Austria, or Switzerland, the Nightjet is IMHO the best sleeper train in the world on balance. Between very reasonable fares, high hotel rates in the cities it serves, and mostly new rolling stock, it's a bargain.
- If you live on the East Coast or Midwestern US, there are several Amtrak services that are reasonably priced when booked well in advance (3-6 months). The City of New Orleans (from Chicago) or the silver services (two different NYC - Florida trains, but they take different routes through NC, SC, and GA) have much more reasonable fares than the Western routes.
- You can often get a good deal on Via Rail in Canada; they still allow you to book a single berth, and they regularly release promo fares for specific dates. The deals are available at https://www.viarail.ca/en/offers/sleeper-plus-class-deals/ and you can scroll down to see the dates and routes that there are savings on. The best deals are from the major cities in Canada (especially Montreal) to points East on the Ocean - you can get a discount private cabin from e.g. Montreal to Halifax, but you're SOL if you want to go to Vancouver in anything other than a berth. Book a Corridor to get to Montreal. These are best booked close-in, unlike Amtrak.
However, if you have the means, book a room(ette) on the Empire Builder in winter. It's simply incredible.
Japan Sunrise Night Train is extremely popular and tourist need to book them several weeks in advance to get a ticket [1]. You can use Japan Rail Pass card for the nobi-nobi economy seats but need to pay extra for the private compartments.
[1] Night Trains:
https://www.japan-guide.com/e/e2356.html