Akan-Mashu National Park: Hot springs and caldera lakes



Akan-Mashu National Park (sometimes also “Akan National Park” or “Akan Mashū Kokuritsu Koūen”) is in East Hokkaido, North Japan. On a map you can find the national park between the Tokachi area where the city of Obihiro is located, and Shiretoko Peninsula.

Akan-Mashu National Park is famed for its large and clear caldera lakes, Lake Akan, Lake Mashu and Lake Kussharo. The area is also known for its volcanic activity that is visible in the form of hot springs, sleeping volcanoes and bubbling mud fountains.  Japan’s largest Ainu Kotan or village is located by Lake Akan in Akan-Mashu National Park. Ainu are the indigenous people of Japan and Russia.

On this column, you can find travel inspiration and off the beaten path activities in the stunning Akan-Mashu National Park of East Hokkaido, North Japan.


Interested in national parks of Japan? Feel free to check our recommended itinerary full of off the beaten path adventures: Four National Parks and Wildlife in Late Spring East Hokkaido

Lake Akan: Onsen town inside a national park

Let us start with Lake Akan. Lake Akan is known as Akanko (or Akan-ko) in Japanese. Most Lake Akan visitors stay at the village-like hot spring resort that is at the south side of the lake. The onsen town is technically part of Kushiro, but it is around 70 kilometers inland from Kushiro city that is located by the North Pacific Ocean.

Like many places in Hokkaido and Japan in general, Lake Akan is a volcanically active area. Lake Akan itself is a caldera lake that was formed in a large eruption approximately 6000 years ago. Akan onsen town is located right between Mt. Meakan and Mt. Oakan of the Akan Volcanic Complex.

One of the most pleasant manifestations of volcanic activity are hot springs or “onsen” in Japanese. Onsen are extremely popular among Japanese. Many people dedicate their vacation solely to natural hot springs. Actually, there are hot spring hotels that do not have a shower or bath at all in their guest rooms! There are both luxurious hot spring hotels and small and cozy Japanese inns in Lake Akan hot spring town. Some accommodations have an open air bath with a stunning view of the lake!

Small mud volcanoes or “Bokke” are an interesting specialty of the Lake Akan area. You can have a little stroll to the eastern side of the town to the tip of a small peninsula. There you can find these steaming, bubbling mud ponds hidden inside the forest or right at the edge of the grand lake. These mysterious little volcanoes make you feel the power of Mother Nature and the volcanic land right beneath you. The caldera lake Lake Akan is also famous for another unusual natural phenomenon: Huge green algae balls or “marimo”.

Marimo: Culturally significant giant algae balls

Marimo is a large algae ball that can only be found in a few places in the world. Lake Akan has good conditions for the formation of marimo. In fact, the marimo of Lake Akan are the largest in the world. These “Japanese moss balls” can be around 20–30 centimeters (8–12 inches). They are not only large, but also of a respectable age: It can take 100 years for a marimo ball to reach this size!

The tourist boats cruising around Lake Akan make a stop to appreciate the marimo at a special observation center. Actually, the algae is so celebrated, that there is even an infamous mascot of Hokkaido inspired by the algae balls: “Marimokkori”. This green superhero has a suggestive bulging in his superhero boxers (“Mokkori” in Japanese means bulging). You can find Marimokkori themed key holders and sweets that make an interesting Lake Akan souvenir.

At Lake Akan tourist shops you may also find marimo moss balls sold as “pets”. Gathering the algae from Akan Mashu National Park is not allowed, so these particular algae balls are actually not from the lake.

Marimo has cultural importance for the Ainu people. An annual Marimo Festival of Lake Akan is an important event that gathers Ainu from all over the island in October. Among other things the festival includes a beautiful ceremony and a parade featuring charming traditional costumes.


Interested in Ainu culture? You might enjoy reading Shiraoi: The town of the Ainu

Akan Ainu Kotan

On the shore of Lake Akan, in the same area as the hot spring facilities there is the largest Ainu Kotan in Japan. Kotan means settlement or village in the Ainu language. Ainu are the indigenous people of Japan and Russia. Ainu have lived in Hokkaido, including the Lake Akan area long before first “Wajin” or Japanese from the main island immigrated to the island.

The Ainu language is an endangered language; There are very few people who can speak the Ainu language and most of them are elderly. In present day Hokkaido most Ainu individuals use Japanese as their everyday language, but for instance songs and tales in the Ainu language are passed down as a oral tradition.

It is believed that many individuals with Ainu roots are not even aware of their heritage, since many parents chose to not let their children know about their cultural background to avoid being discriminated. In fact, Ainu were officially recognized as “an indigenous people with a distinct language, religion and culture” only in 2019. In recent years it has become more acceptable and even trendy to study the Ainu language and culture, but still the Ainu culture is often not very visible in the everyday life or the city streets of Hokkaido. There are individuals who work in the travel industry partly because they wish to actively practice Ainu traditions and be true to their heritage in their everyday lives. The movie Ainu Mosir (2020) pictures the identities, reality and coexistence with the tourism industry of the Ainu people through the eyes of a young boy living in Akan Ainu Kotan.

Ainu culture and travel: Respect and support

Some 120 people live in Akan Ainu Kotan. Many of them work in the travel industry, selling handmade souvenirs, arranging performances or teaching traditional arts to travelers.

On the other hand, it may feel that the whole Kotan has been turned into a tourist attraction that portrays a version of Ainu culture, that travelers want to see. But in the end, this is the home of the Ainu living at Lake Akan and many locals are very proud of their way of living.

Tourism can be an important tool to let new generations know about Ainu culture. Tourism can also be an important motivator to pass on the traditions. Working in the travel industry, inspiring Ainu individuals can have an active part in shaping the discourses of Ainu culture in modern Japan. Besides visiting souvenir shops or performances you can yourself learn about the Ainu way of life up close and personal, get to know interesting individuals and the traditional knowledge. Ainu were formerly hunter-gatherers, so it is no wonder that nature has an extremely important position in the culture. Among other things, at Lake Akan you can join a guided nature walk with an expert guide with Ainu roots and learn about the local flora and fauna through the Ainu culture.

It would be our pleasure to help you make more sustainable choices that support and respect the locals and their lifestyle in their own terms.

Kawayu Onsen: hot springs at the base of a sulfur volcano

Some 50 kilometers northeast from Lake Akan you can find the two other caldera lakes of Akan-Mashu National Park: Lake Kussharo and Lake Mashu. Between these two there is Teshikaga town and Kawayu Onsen. “Kawayu” means literally “hot water river”. As the name suggests, in the middle of Kawayu Onsen town there is a small river called “Yu River” with warm hot spring water. Even if a public bath feels too extreme, you can enjoy the special hot spring water by dipping your feet into the warm foot bath in the middle of the town. (Please note that many of the hot spring facilities are around 3 kilometers north from the Kawayu Onsen train station.)

The hot spring of Kawayu is not your basic onsen. The water used in the hot spring facilities is high in sulfur! Japanese consider the smell of sulfur a sign of high quality onsen, so Kawayu really is top class (The smell of sulfur is a little like rotten eggs for the untrained nose, but you learn to make the association soon enough).

The sulfur in the water comes from nearby volcano, Mt. Io (Iō-zan, literally “Sulphur Mountain”) in Japanese or Atosanupuri (“Naked Mountain”) in the Ainu language. If you decide to try out the acidic bath, you may be surprised to find a warning sign saying that you should not stay too long in the water – Or else your nails could melt away!

Besides sulfur hot springs, Kawayu Onsen is also famous for something maybe a little unexpected: Sumo. Kawayu is the home town of the legendary sumo wrestler and long time champion Taiho Koki. While you are in the area, it could be interesting to pay a visit to the local sumo museum. You can also find some sumo statues in the town. And there is even a sumo rink in front of a Shinto shrine!

The steaming silhouette of Mount Io is a great sight. At the base of Mt. Io there is an observation area where you can take cool pictures of the fumaroles. The boiling hot vents are bright yellow because of the sulfur. You can even buy eggs that have been boiled with the naturally hot water of the area.

You can do some light hiking in the nearby nature trails. The area is known for its alpine flowers that are especially beautiful in spring. However, to climb to the mountain you need to be accompanied by an experienced guide for safety reasons. Hokkaido Treasure Island Travel can arrange hiking tours to the volcano with our local partners. The view from the top of the steaming mountain is truly worth the climb!

Besides just enjoying a cool hike, a private tour is a great opportunity to get to know an interesting local personality and hear about the local lifestyle and interesting stories of this notorious area. Nowadays Mt. Io is a a popular tourist attraction and a source of high class hot spring water, but the area has a dark past. In the 1880s and 1890s, the precious sulfur was mined by people who were forced to work in very poor working conditions. Many suffered of poisoning and there are reports that around 200 laborers fainted in the hard conditions before the mine had to be closed. Your guide can show you the remains of a rail way that was used to transport the sulfur.

Lake Kussharo: Lake Monsters and Whooper Swans

Only 5 kilometers northwest from the steaming sulfur mountain, there is Lake Kussharo. Lake Kussharo (or Kussharoko in Japanese), is the largest caldera lake in Japan by surface. The lake is sometimes also knows as the Loch Ness of Japan, because since the 1970s there have been reports of a giant lake monster. This imaginary relative of “Nessie” is jokingly called “Kussie” (or Kusshii). You can find a statue of Kussie at the shore of Lake Kussharo.

Lake Kussharo is also known for “Sunayu”, literally hot water sand. There is a beach where you can dig the sand and make your own foot bath. Under the sand is volcanic land, so when you dig a small hot springs will come bubbling from the ground!

Besides mysterious lake monsters, Lake Kussharo is known to attract migrating birds who stop by in winter. Parts of the lake stay relatively warm even in winter thanks to the volcanic activity. The lake is famous among nature photographers as a great location for photographing whooper swans. Hokkaido Treasure Island Travel arranges all inclusive photography tours in East Hokkaido. Feel free to contact us for more information.

Volcanic canoe picnic to the tip of Wakoto Peninsula

At the southern edge of Lake Kussharo, there is Wakoto Peninsula. The peninsula area has some hidden onsen hot springs, so bring your swimsuit, if you like the idea of open air bath. The peninsula is not that large, but the forest is deep and sometimes deer can be spotted hopping around.

At the tip of Wakoto Peninsula, hidden by the thick forest is an unbelievable sight: Steaming hot “Oyakotsu Hell”, a place where the lake boils and steam rises from the ground. This intriguing spot is surrounded by steep cliffs from the peninsula side, so it can only be reached from the lake.

One of our most loved exclusive activities is a canoe picnic tour to the tip of Wakoto Peninsula in Lake Kussharo. After some nice canoeing and appreciating the breathtaking views, you will land in the steaming hell (be careful if you wish to take your shoes off). While you explore, your guide will prepare some boiled eggs and steamed foods such as corn and oysters making use of the hot water and land.

A handmade lunch tastes amazing after some exercise with good company and a panoramic national park scenery spreading around you!

Lake Mashu: The Lake of the Gods

On the opposite side of Lake Kussharo from Mt. Io and Kawayu Onsen, there is Lake Mashu (Mashū-ko or Kamuy-to). This deep and clear caldera lake is at the bottom of a steep crater. The lake is one of the clearest lakes in the world, but because of its shape and location it is often covered by thick fog.

The lake can be appreciated from several observation decks, but descending on the shore is not allowed. In winter, we can arrange a snowshoe hiking tour to the edge of the crater.

On the edge of the mysterious caldera lake stands Mt. Kamuy, or Mountain of the Gods in the Ainu language. Lake Mashu itself has also been called Lake of the Gods and Lake of the Devil. Standing at the steep edge looking down at the depths of this bewitching lake, it is easy to understand why.


Recommended itinerary for winter: Full Course of Epic Winter Activities in East Hokkaido

From hot springs to unbelievable sceneries, Akan Mashu National Park of Hokkaido, North Japan has plenty to offer. If you feel that Akan Mashu National Park should be on your travel bucket list, let us know!

You might also enjoy reading: Shiretoko: The peninsula at the end of the earth


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