Located between Kussharo-ko and Mashu-ko, the small onsen town of Kawayu (川湯温泉: meaning hot springs river) boasts highly acidic water supplied to the all hotels.
There is a 24-hour free ashi-yu (あし湯: footbath) beside the small river.
(川湯公衆浴場) Onsen enthusiasts should visit this ageing koshu yokujo (bathhouse) and soak in highly acidic water like lemon juice. Bring your own towels and soap. It is closed on Wednesday except August.
Kawayu Eco Museum Center
(川湯エコミュージアムセンター) This wooden building by the onsen town has displays and exhibitions on the lakes, forest and volcanos in Teshikaga. Rental wears and snowshoes are available. There is also a cafe. Behind the museum center, there are short circuit walkways in Sakhalin Spruce Forest. More info www.kawayu-eco-museum.com
Tsutsujigahara Nature Trail
(つつじヶ原ネイチャートレイル) Teshikaga’s most popular nature trail makes an hour hike (2.5km) from Kawayu Onsen to the sulfer mountain Io-zan (硫黄山), surrounded by white iso-tsutsuji (wild rosemary).
From 10 June to 10 July, you can join a 90-minute guided tour (¥500) freely. It starts from Kawayu post office at 6am and return to the onsen by a coach.
From JR Kawayu-onsen Station (川湯温泉駅) on the JR Senmo Line, there are seven buses to the town of Kawayu Onsen 10min; ¥290) beside the Sumo Museum (相撲記念館), and timed to meet trains from 8am to 6pm. The last bus from the train station is at 5.45pm.
From JR Mashu Station, three buses run daily to the town of Kawayu Onsen (37min) via Biruwa and Kawayu-eki-dori near JR Kawayu-onsen station.