Kushiro Shitsugen (Kushiro marsh=釧路湿原) is national park and has the largest marsh wetland in Japan. It is well known as the home of endangered Japanese Cranes (丹頂鶴). JR Hokkaido’s Senmo line goes through this wetland and gives you a great scenery. Kushiro Shitsugen Norokko train (釧路湿原ノロッコ号) is operated on this line from late April to late September. This is the easiest way to enjoy a day excursion in Kushiro Shitsugen from Kushiro. And Kushiro can be reached by Limited Express Super Ozora from Sapporo easily. Both Super Ozora and Kushiro Shitsugen Norokko train are fully covered by Japan Rail Pass.
When you go to South East part of Hokkaido, these trains take you there. Super Ozora and Super Tokachi are operated on same route. Super Ozora connect Sapporo and Kushiro. Super Tokachi connect Sapporo and Obihiro. These trains are very popular and the reserved seats are sold out very often. Especially JR Hokkaido give you a great service in Green car. Sometimes Green car is sold out earlier than Ordinary class. Both trains are fully covered by Japan Rail Pass. So if you have a plan to take these trains, I strongly recommend you to reserve your seat when you exchange your Japan Rail Pass.