The Japanese regional railway JR Kyushu has become the first company in Japan to build a luxury sleeper cruise train, spending close to 3 billion yen (US$29.9 million). The Seven Stars cruise
Cassiopeia is most popular overnight train in Japan. *This train was discontinued in March 2016. Cassiopeia is operated between Ueno and Sapporo.This train is like Japanese version Oriental Express and is the most luxurious in three luxurious overnight trains (other two are Twilight Express and Hokutosei) in Japan.
Having taken sleeper trains in both Japan and Singapore-KL in the distant past, I would recommend the Singapore-KL train over a Japanese sleeper train anytime. Perhaps the newer trains are better, but I found the berths too short and very narrow. Neither Japanese night trains nor night buses give good views of the scenery.
The Cassiopeia sleeper train between Ueno and Sapporo was discontinued a while ago and we didn't get around to use it while it was still running. However, the Wikipedia site linked to a feature that mentioned could re-open as a cruise train. I also saw a NHK feature once that showed that it running as a packaged tour by a private operator (albeit only as far as Aomori).
West Japan Railway, which serves Osaka and other areas in the western part of the main island of Honshu will launch its version of the luxury sleeper train called Twilight Express Mizukaze in June.
Your Japan Rail Pass is valid for travel on sleepers. Seats are free for Japan Rail Pass holders, while using a bunk or private room will cost you an additional discounted fare. Seats are free for Japan Rail Pass holders, while using a bunk or private room will cost you an additional discounted fare.