Most Japanese festivals honour a deity, a warrior or a harvest. This one honours a ball of algae — and it is one of the most quietly moving things you can witness in autumn Japan.
From 8 to 10 October 2026, the hot-spring town on the shore of Lake Akan in eastern Hokkaido holds the 77th Marimo Festival (まりも祭り). It is led by the residents of Akanko Ainu Kotan, the largest Ainu settlement in Japan, and it exists for a reason that has nothing to do with tourism: in the 1940s, the lake's marimo were being stripped out and sold as souvenirs, and the Ainu community organised a ceremony to bring them back and protect them. Three-quarters of a century later, that rescue mission is still the backbone of the festival.
What marimo actually are
Marimo are spherical colonies of green algae that roll slowly along the lake bed, shaped into velvety balls by gentle currents. They grow roughly 5 millimetres a year, so the largest specimens in Lake Akan — over 20 centimetres across — are older than most of the buildings around the lake. They occur in only a handful of lakes worldwide, and Lake Akan's are designated a Special Natural Monument of Japan. Wild marimo cluster in Churui and Kinetanpe bays at the north end of the lake, both off-limits to visitors. To see them, take the sightseeing boat to Churui Island, where the Marimo Exhibition Centre keeps living specimens in cold tanks with underwater viewing windows. The round trip takes about 85 minutes including the island stop.
The three days
Day one — the welcome. Divers retrieve a small number of marimo from the lake bed and they are carried to the kotan, where the community performs kamuy nomi, a prayer to the spirits of the lake. Ainu elders lead the ritual in the Ainu language; the atmosphere is ceremonial rather than festive.
Day one, after dark — the torch procession. This is the image most people come for. A column of torches winds through Akanko Onsen along the lakeshore, with Ainu dancers and drums, the flames doubled in the black water. Dress warmly: nights in early October at this altitude drop close to freezing.
Day two — dances and the marimo dance. The kotan performs Ainu koten buyo, the traditional dance forms inscribed on UNESCO's Intangible Cultural Heritage list in 2009, including the crane dance and the sword dance. Performances run through the afternoon at the village and its open plaza.
Day three — the return. The most photographed moment. The marimo are placed in a decorated vessel and carried out onto the lake by chip, traditional Ainu dugout canoes, accompanied by a flotilla of boats. After a final prayer, the algae balls are lowered back into the water where they were found. Then the town sees the visitors off.
Timings shift slightly year to year and the lake-borne ceremonies are weather-dependent. Confirm the schedule with the Akanko Onsen tourist association or your hotel front desk the day before.
Akan Ainu Art Week
Running in parallel from 8 October, Akan Ainu Art Week turns the kotan into a working gallery. Akan has been a centre of Ainu woodcarving for generations, and the week puts contemporary Ainu artists — carvers, textile makers, embroiderers working kaparamip appliqué and chikarkarpe patterns — in front of visitors with exhibitions, open studios and hands-on workshops. It is the best chance of the year to buy directly from the maker rather than from a shelf, and to hear how a motif that looks decorative is in fact a protective design. Workshop slots are limited and some need advance booking.
Evenings at the kotan
The kotan's Onnechise theatre stages Ainu dance nightly, paired with Lost Kamuy, a digital-art performance that projects the story of the Ezo wolf around the dancers. Out in the forest above town, Kamuy Lumina is a night walk that retells an Ainu folktale through projection mapping along a lakeside trail; it usually operates into early November, but check dates before you plan around it.
The town itself is a classic Hokkaido onsen resort — large lakeside baths, most with open-air sections looking straight at Mount Oakan across the water. A rotenburo at 5°C air temperature is one of the better arguments for visiting Hokkaido in October.
Autumn colour and the volcanoes
Early to mid-October is peak koyo at this altitude. Lake Akan sits in a caldera in Akan-Mashu National Park, ringed by birch, Mongolian oak and Japanese rowan turning at once, with the cones of Mount Oakan and the still-active Mount Meakan behind them. Two easy walks start in town: the Bokke trail, a 20-minute boardwalk loop through forest to bubbling mud pools where volcanic gas pushes up through grey clay, and the lakeside promenade toward the eco-museum centre, which is where most people see their first Ezo squirrel. Serious hikers climb Mount Meakan (around 7 hours return) — check volcanic alert levels first.
A day in the Kushiro Wetlands
Give yourself an extra day for Kushiro Shitsugen National Park, Japan's largest wetland and a Ramsar site, about 90 minutes south. In autumn the reed beds turn gold and the crowds are gone. The Hosooka Observatory gives the wide view over the meandering Kushiro River; the Onnenai boardwalk takes you level with the marsh. Red-crowned cranes — sarurun kamuy, the marsh god, in Ainu — are resident year-round, though the famous winter dancing displays come later. Canoe operators run quiet morning paddles down the river when conditions allow. In Kushiro city, end at the Washo Market with a katte-don: buy a bowl of rice, then walk the stalls choosing your own sashimi to pile on it.
Getting there
Fly to Kushiro (Tancho Kushiro) Airport from Tokyo Haneda in about 100 minutes; airport buses reach Akanko Onsen in roughly an hour. From JR Kushiro Station, Akan Bus takes about two hours. Memanbetsu Airport near Abashiri is a viable alternative if you are combining with the Shiretoko side. A rental car is the best option overall — the roads through the caldera are the point, not just the transfer — but be aware that deer on the road at dusk are a genuine hazard here.
Accommodation in Akanko Onsen fills for festival nights. Book by late September, and if the lakeside hotels are gone, Kushiro city with a day trip up is a workable fallback.
A note on how to be there
This is a living indigenous ceremony, not a performance staged for visitors. Watch the prayer sections quietly, ask before photographing individuals, and if you buy a carving, ask the artist about it — they would rather talk than sell in silence.
Image: Lake Akan, Kushiro, Hokkaido by 663highland, CC BY 2.5, via Wikimedia Commons
