Lake Onneto: The Color-Changing Lake Below the Akan Volcanoes

By Chaporo, a Sapporo local Published
Lake Onneto: The Color-Changing Lake Below the Akan Volcanoes

Quick answers

  • A quiet forest lake whose color shifts from blue to green to emerald
  • Mt. Meakan and Mt. Akan-Fuji stand right behind it
  • About 20 to 40 minutes by car from Lake Akan Onsen
  • No toilet or shop at the viewing deck, and a weak phone signal

Lake Onneto is a small lake in the forest about 20 to 40 minutes by car from Lake Akan Onsen, and one of the quietest places in Akan Mashu National Park. Its water changes color with the weather, the time of day and the angle you look from, from blue to green to emerald, and from the viewing deck you see two volcanoes, Mt. Meakan and Mt. Akan-Fuji, standing right behind it.

What is Lake Onneto?

The lake formed when an eruption of Mt. Meakan dammed a river. Its name is said to mean "old, large lake" in Ainu. It is very clear, about 2.8 meters deep on average and 9.8 meters at its deepest, and at about 623 meters above sea level it is the highest lake around Lake Akan. The clear water, the shape of the land and the way the light falls together give it its unusual colors.

The view of Mt. Meakan and Mt. Akan-Fuji

The viewing deck at Lake Onneto, with Mt. Meakan and Mt. Akan-Fuji beyond the lake

From the viewing deck, Mt. Meakan and Mt. Akan-Fuji stand side by side straight ahead. The lake, the forest and the mountains line up, with almost nothing man-made in sight, and it feels bigger than it looks in photos. When I was there, I kept stopping just to look.

Mt. Meakan and Mt. Akan-Fuji over Lake Onneto in autumn

Each season looks different: autumn leaves, fresh green in early summer, snow in winter. On a sunny morning the color of the water seemed at its best.

Walking by the lake

There are walking paths along the shore, with several routes of different lengths, so even a short visit gets you into the forest. Visitors are asked not to swim or paddle canoes, to keep the lake quiet and protected: come for a quiet walk, not a swim.

On a road trip

Lake Onneto is easy to fit in on the way from Lake Mashu to Lake Akan. The order that worked well for me was Lake Mashu, the 900 Grassland viewpoint, the Sogakudai and Sokodai lookouts, Lake Onneto, then Lake Akan Onsen for the night.

Lake Akan: The Sightseeing Cruise, Marimo and Ainu KotanA local's guide to Lake Akan in eastern Hokkaido: the sightseeing boat to Churui Island, the marimo moss balls, Akanko Ainu Kotan, and how to fit the lake into a road trip. Lake Mashu, Lake Kussharo and Lake Akan: A Local's Eastern Hokkaido Road TripA two-night road trip around Lake Kussharo, Lake Mashu and Lake Akan to the Kushiro Wetland, from a Sapporo local who drove it: the order that works, what each lake is like, the boat to the marimo, and weather and driving tips.

Things to know before you go

  • There is no toilet at the viewing deck. Use the public toilet at Meakan Onsen on the way, or the campground toilets (June to October). A small rest house by the campground sells light snacks and drinks from June to October; otherwise bring your own.
  • The phone signal is weak, so download your route before you go.
  • The lake looks very different with the weather, so if you have time, wait a little and watch it change.

FAQ about Lake Onneto

Q1. How far is Lake Onneto from Lake Akan?

About 20 to 40 minutes by car from Lake Akan Onsen, on Route 241 and Prefectural Road 949.

Q2. Why does Lake Onneto change color?

Its clear water, the surrounding landscape and the angle of the light combine to make it look blue, green or emerald depending on the weather and the time of day.

Q3. Can you swim in Lake Onneto?

Visitors are asked not to swim or paddle canoes, to keep the lake quiet and protected.

Q4. Are there toilets at Lake Onneto?

Not at the viewing deck. The nearest are at Meakan Onsen (all year) and the campground (June to October).