While I have never been there, Japan appears to have a wide variety of rail options. I recently came across the
Cassiopeia, described as "a luxury overnight limited express train" operated by JR East between Tokyo and Sapporo. While not particularly fast (over 16 hours to cover some 700+ miles), it has some of the most luxurious equipment I've ever heard of on regularly-scheduled services, including a modern observation-lounge at one end, and a full double-bed suite at the other!
[
en.wikipedia.org])
[
www.jreast.co.jp]
[
www.jreast.co.jp]
[
www.jreast.co.jp]
[
www.jreast.co.jp]