57km of shoreline and up to 117m deep, Kussharo-ko (屈斜路湖) is Japan’s largest caldera lake. Visitors enjoy getting into the kon’yoku onsen roten-buro (混浴温泉露天風呂: mixed open-air baths: you will need a bathing suit), camping, fishing and hiking around the pleasant shores. Summer and weekends are often bustling with holidaymakers, plan your trip during the weekdays.

Points of interests on the Lake Kussharo

Getting There

It is recommend you to explore the shores with your own wheels. Most attractions can be reached by the seasonal Kussharo Bus (屈斜路バス) for Teshikaga Eco-Passport (弟子屈えこパスポート) holders.

More info about Teshikaga Eco Passport www.eco-passport.net

Wakoto Onsen

(和琴温泉) At the base of the Wakoto Peninsula (和琴半島), there is a free mixed open-air bath (24hrs) with gender-segregated changing facilities and a campsite.

A few hundred meters away from the open-air bath along the peninsula’s southern shore, you will find a one-room free bathhouse of Wakoto Kyodo Yokujo (和琴共同浴場) with mixed bathing only (it is very hot and a shared changing area: not recommended for women).

Kotan Onsen

(コタン温泉) A man-made rocky mixed open-air bath by the lake, this scenic onsen is about 150m north of the Kotan Ainu Folklore Museum. In winter you can see swans from a bathtub. There are changing rooms, bring a bathing suit. The bath is maintained on Tuesday and Friday (8am-4pm) by locals.

Near the open-air bath, there is also a small bathhouse (Noon-9pm, to 10pm Jul-Aug; Closed Wed; ¥300) of Kotan Kyodo Yokujo (コタン共同浴場) with gender-segregated facilities.


(池の湯) Tucked away within the lakeside forest, Ike-no-yu is Kussharo’s largest mixed open-air bath like a lukewarm pool (the water temperature is around 38C).

The gateway is about 4km north of Kotan Onsen, look out for the small sign marked ‘Matsuya Ryokan (まつや旅館)’ on your left. The bath is 200m from the lakeside road. There are changing rooms, but night-time lighting is not available. The best bathing season is late spring to early autumn.


(砂湯) On the eastern shores of Kussharo-ko, you can find hot water in the sand here. Dig a hole for your own natural hot pool. Suna-yu is a popular spot especially group tourists and campers, you should wear a bating suit if you want to soak in hot water. There are no bathtubs and changing rooms.