Shiretoko is one of UNESCO World Heritage Sites in Japan. There are falls, lakes and onsen. Shiretoko is one of the best place to enjoy the nature of Hokkaido. I will share the information about access Shiretoko.
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Utoro is the biggest town in Shiretoko peninsula. Most of tourists stay overnight there and visit Shiretoko five lakes, falls and enjoy outdoor activities. Rausu is located at the other side of peninsula. You can visit there if you like. Both Utoro and Rausu are connected by bus but it runs summer time only. This road is closed in winter time.
Access from Abashiri via Shiretoko-Shari
Shiretoko cannot be accessed by only train trip. The nearest station is Shiretoko-Shari. Both JR Pass and Hokkaido Rail Pass cover the trip to Shiretoko-Shari. But after arrival at Shiretoko-Shari, you have to take the bus and this bus is not covered by any rail passes.
You can find the train timetable of both Limited Express Okhotsk and Senmo line local train at JR Hokkaido official site:
You can find the timetable of bus for Shiretoko-Shari to/from Utoro in the link below. Utoro is one of the bases in Shiretoko peninsula.
You also can find the timetable of tourist bus. This is a guided bus for overseas tourist. You can visit Shiretoko as day trip by this bus service.
Access from Kushiro
You can take JR Senmo line local train from Kushiro to get Shiretoko-Shari. Limited Express Super Ozora connects Sapporo and Kushiro.
You also can access Rausu in Shiretoko from Kushiro by bus directly. However the destination is Rausu. Rausu is located at southside of Shiretoko peninsula.
Unfortunately the timetable of the bus service between Kushiro and Rausu is available in Japanese only. You can find it in the link below:
I hope this post helps you to build your trip plan to Shiretoko.