The Nihonkai (日本海, "Sea of Japan") was a seasonal overnight train which was operated by the East Japan Railway Company (JR East).

From the start of the March 17, 2012 timetable revision, regular operations of the Nihonkai were discontinued, with services operating during busy seasonal periods only.

[2] While JR East has not formally announced its discontinuation, no services have operated since January 2013, Sometimes it either connect to Sapporo or Hakodate.

The journey time was around fifteen hours, depending on the exact route taken.

The Nihonkai was hauled by a JNR Class EF81 electric locomotive based at Tsuruga and operated by JR West Fukui Operations Center.