Sunayu & Lake Kussharo | Hokkaido's Secret Winter Swan Sanctuary

The first thing you see, standing at the lakeshore, is a sheet of white.

Not snow — swans.

Sunayu sits on the shore of Lake Kussharo, where geothermal heat wells up from the lakebed and keeps this stretch of water ice-free even in Hokkaido’s coldest month, January. Whooper swans fly here to winter every year precisely because of this unfrozen patch of water.

At peak there are several hundred of them.

The swans are almost unafraid of people. Walk down to the water and they just turn their heads to glance at you, then go back to paddling, preening, dipping their heads under to feed. The nearest are two or three steps away, so white they almost glow.

Mt. Mokoto rises in the distance, snow on its summit, a thin morning mist drifting over the lake. A swan glides across, and the scene is as still as a painting.

Step onto the sand and it’s warm. Even when it’s below freezing outside, the sand here always carries the warmth of the earth’s heat — which is where the name Sunayu (“sand hot spring”) comes from.

The Story of This Place

Lake Kussharo is the largest caldera lake in Japan, and this sheet of water took shape roughly 30,000 years ago; an even earlier eruption around 120,000 years ago threw out volcanic ash that blanketed nearly all of Hokkaido except the land west of Sapporo. The lake's name comes from the Ainu word Kutcharo, meaning \"throat\" or \"outflow\" — for this is the very source of the Kushiro River, and Japanese settlers later transcribed the sound with the characters read \"Kussharo.\" The name Sunayu (\"sand hot spring\") is just as literal: geothermal heat seeps up through the lakebed, so if you dig into the sand with a shovel, hot water wells up — in places it can climb close to 50°C.

For all its gentleness, though, the lake has a temper. After the Kussharo earthquake of 1938, sulfur is thought to have vented from the lakebed, and the water turned acidic — around pH 4 — killing off almost all of its fish. To this day, Lake Kussharo holds no fishing rights. The island at its center, Nakajima, is the largest island-within-a-lake in Japan, some 5.7 square kilometers, and is itself a volcano.

As for how Nakajima came to be, a local Ainu tale is still passed down. As the story goes, a monstrous amemasu (a great white-spotted char) once lived in the lake and made trouble, until an Ainu hero caught it and tied it to a mountain on the shore; thrashing in fury, the giant fish tore the whole mountain out by its roots and sent it crashing into the water — and that, they say, became Nakajima. In more recent times the lake has gained another star: a legendary creature called Kusshie. As the tale is told, one winter's day in 1972 a driver on the lakeside highway spotted a dark shape \"like an overturned boat\"; the following summer, about forty middle-school students saw it together during an excursion on Mount Mokoto, and Kusshie's fame spread across Japan. And here's the thing — the mountain we were gazing at while watching the swans is that same Mount Mokoto. Skeptics have their point, of course: after the lake turned acidic in 1938 it can barely support fish, so what would feed a creature that size? Fact and legend simply sit side by side here, and you're left to make of them what you will. Standing on the sand at Sunayu, warm spring water rising under your feet, Mount Mokoto and the island at the lake's heart lying quietly in the distance, you realize those old stories aren't so far from where you're standing after all.

Swan-watching times and season

Whooper swans start arriving in late November; December to February is when there are the most, and they begin heading north again after mid-March. Numbers are highest at dawn, and the swans also rest along the shore toward evening. Besides swans there are ducks and other migratory birds. There’s a feeding platform at Sunayu’s shore, and staff occasionally scatter grain — when they do, the swans gather in great numbers and it gets wonderfully lively.

A one-day Lake Kussharo itinerary

Sunayu pairs perfectly with Lake Mashu and Mt. Iō (Atosanupuri) for a single day: in the morning, admire Mashu Blue from Lake Mashu’s First Observation Deck, then see the active volcano’s steam vents at Mt. Iō, have ramen in Teshikaga at midday, come to Sunayu for the swans in the afternoon, and drive along the western shore of Lake Kussharo toward evening, stopping at the Omiwatari (ice ridges) and the lakeside Kotan Onsen / Ike no Yu open-air and foot baths on the west shore. It’s about 100 km of driving in all.

Getting there and things to note

Sunayu has no public transport — you’ll need to drive. The nearest airport is actually Memanbetsu (about 1 hour); from Kushiro Airport it’s about 2 hours (89 km, longer when the roads ice over), and from Obihiro about 3 to 3.5 hours (roughly 180–220 km, a long haul that’s slower still in winter). Winter roads are icy, so when renting a car make sure it has four-wheel drive or snow tyres (standard winter equipment at most rental companies), and check whether the car park is cleared of snow. Parking at Sunayu is free. Winter car rental in Hokkaido can be booked via Klook.

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Around Lake Kussharo

Lake Kussharo is Japan’s largest caldera lake, and beyond Sunayu the shore has a few more spots worth visiting: Mt. Iō (walk right up to the steam vents, free), Bihoro Pass (a mountain pass with a full view of Lake Kussharo — especially recommended for the morning sea of clouds), and Kawayu Onsen (a sulphur spring that leaves the soles of your feet smooth). Combined with Kushiro Wetland, this area makes a 2–3 day deep dive into eastern Hokkaido. A rental car is recommended — public transport out here is sparse.