Hardy bathers braving bitterly cold temperatures in nothing but a bikini or pair of trunks have been enjoying the exhilarating experience of a Finnish pastime known as "avanto" in Hokkaido.
The extreme winter hobby involves plunging into a hole carved out in the ice covering of lake to cool down after a sweating it out in a lakeside sauna hut.
This is the second year that Tokachi sauna council, a body established to contribute to regional promotion through saunas, has opened the facility at Lake Kuttari to the public.
The first day of the season on Jan. 7 saw 13 people visit the facility, which has drawn enthusiasts from both inside and outside Hokkaido.
After warming up in a sauna, visitors headed for the lake to jump into the hole and submerge themselves in the frigid water, replicating the avanto practice of bathing in cold rivers.
The hole is created by cutting a square measuring roughly two meters square into a 30-centimeter-thick sheet of ice and also features a safety net and ladder.
In addition to the avanto, visitors can enjoy blue skies and the view of snow fields atop a rotating "ice carousel" created by cutting out a circle in the ice.
"The extreme temperature difference and the great outdoors. It's the ultimate sauna," said Yuki Yanase, a visitor from Utsunomiya.
The facility is open through March 12, with the Tokachi sauna council accepting reservations through its website.