Dozen of night trains used to be running in Japan. However, there are only two regular night trains now.
Sunrise Express debuted in 1998, new concept of night train in Japan. The train has fixed consists(train set) with sleepers and carpet car(no walls between passengers and you sleep on the carpet), no locomotive to pull or push the cars. JR's first night train to abolish couchettes. Then, showers are also equipped.
During BLUE TRAIN era, passengers preferred cheaper way, sleeping on couchettes. However, after air tickets dropped down and long distance buses appeared, JR lost many clients and shifted to high class night trains as like Sunrise Express which led not to consist couchettes.
There are two Sunrise Express. Sunrise Izumo and Sunrise Seto. Izumo connects Tokyo and Izumo-shi, the gateway for Izumo shrine in Shimane prefecture. On the other hand, Seto connects Tokyo and Takamatsu, the major city in Shikoku island. Izumo is popular for female passengers who want to visit Izumo shrine to pray for their marriages and Seto crosses the longest bridge on Earth.
The both trains are connected between Tokyo and Okayama stations. Later Izumo runs on Hakubi line stopping at Bicchu-Takahashi which is close to Bicchu-Matsuyama castle. Seto continues to Seto-Ohashi line toward Shikoku island.
Then, Sunrise Express is convenient for traveler who does not want to overnight in Osaka area but want to be in Tokyo next early morning. Sunrise Express calls at Osaka station at 00:32 and departs at 00:34 and heads Tokyo, therefore you can spend long time in Osaka area or you can take the last Shinkansen from Hakata or Hiroshima and change to local train at Shin-Osaka before getting on at Osaka station. However, watch out that Sunrise Express bound for Izumo-shi/Takamatsu will not call at Osaka station! The first stop after Hamamatsu is Himeji.
For Japan Rail Pass holder, you have to pay both supplements, limited express supplement and fee for sleepers. Carpet car should be without any extra fee.