The mist swirling around makes it feel like a fairyland — the stunningly clear view of "Lake Mashu."

Text and photos by /kuma

Lake Mashu is Japan's clearest lake, and when the weather is clear, the blue reflected on the water surface is known as...

Because of this unique blue and its almost impurity-free clarity, it is also called the "Mashu Sapphire." It was listed as a Hokkaido Heritage in 2001. Mist is a famous feature of Lake Mashu, as the area is shrouded in fog year-round. So seeing Lake Mashu on a clear day is considered very lucky — but this luck comes with an ominous legend, creating a contradiction between fortune and misfortune.

There are four observation decks at Lake Mashu. Except for the Lake Mashu Rear Observation Deck, which is located on the opposite side, the other three are all on the same side, although the Second Observation Deck is currently closed. On the day, after leaving our accommodation at Kawayu Onsen, we headed straight for Lake Mashu. The road was winding with beautiful scenery along the way. The First and Third Observation Decks of Lake Mashu are about 2 kilometers apart. The First Observation Deck has more parking spaces and is the most visited, while the Third Observation Deck has only about 30 parking spots. Due to its height and lack of shelter, it offers a panoramic view of the entire beauty of Lake Mashu.

On the way to the First Observation Deck of Lake Mashu, you will first pass the Third Observation Deck. It is actually quite recommended to stop here. From the parking lot, you still need to walk a bit to reach the viewing platform. In addition to enjoying the sapphire-like lake from different angles, walking along the alpine ridge is also quite thrilling.

Lake Mashu is located in eastern Hokkaido and is part of Akan National Park. It was formed approximately 7,000 years ago as a small caldera caused by a volcanic eruption, and is surrounded by cliffs about 600 meters high. At its southeastern end lies Mount Mashu, known in the Ainu language as the “Mountain of God.” The circumference of Lake Mashu is about 20 kilometers, and its deepest point is approximately 212 meters. Since there are no rivers flowing into or out of the lake, the water remains crystal clear and mirror-like. However, in recent years, pollution from nearby aquaculture and other activities has affected the clarity of Lake Mashu.

At the Third Observation Deck, besides admiring the deep blue of Lake Mashu, you can also gaze at the scenic views of Mount Iou, Mount Marukoma, and Lake Kussharo on the other side.

Next destination: Mount Iou. First, enjoy another perspective of it from the Lake Mashu Observation Deck.

Besides seeing densely packed trees covering the mountainside, the pastoral scenery below is also enchanting.

Walking along the path to the viewing platform, you can see several gracefully shaped trees dancing alone or in groups.

The trees atop the mountain, not yet in leaf for spring, are neatly aligned as if outlining the edge of the mountain.

The path from the Third Observation Deck parking lot to the viewing platform is accompanied by different scenery on both sides. After seeing Lake Mashu from the First Observation Deck, this spot is truly the best place to admire the lake, with relatively fewer tourists.

By the way, there is a warning sign at the Third Observation Deck parking lot about vehicle theft, so if you’re driving, please take valuables with you and stay cautious.

Speaking of which, when I got out of the car, I found the bumper covered in bugs. It was the first time I encountered such a thing while driving in Japan. No matter where I drove or how far, the car was always clean when I returned it. But here around Lake Mashu, I was a bit surprised.

Leaving the Third Observation Deck of Lake Mashu, we arrived at the First Observation Deck. Unlike the free parking earlier, parking here costs 500 yen, and the parking fee is a shared ticket with Mount Iou.

Lake Mashu was once the clearest lake in the world in Showa 6 (1931).

At the First Observation Deck, the many trees create some visual obstructions, making it a bit difficult to get a full view of Lake Mashu. Coming here from the Third Observation Deck, the sky had gathered quite a few clouds in just a short time, and this reflection on the water made it hard to leave.

When talking about Lake Mashu, one cannot fail to mention the small island in the lake, Kamuishu Island. This island rises 30 meters above the water surface but is actually the top of a volcano that reaches 240 meters in height. This small protrusion is referred to as the “Dimple of Lake Mashu,” a rather adorable association.

Kamuishu Island means “The Old Woman Who Became a God” in the Ainu language. There is also a legend associated with this place: On the night the Ainu people held a bear ceremony, a war broke out. The defeated side was completely wiped out, and an old woman escaped with her grandson. During the escape, she became separated from her grandson. As she searched, she came to the shores of Lake Mashu. She had originally planned to stay just one night, but overwhelmed by sorrow and exhaustion, she could no longer go on. As the days passed, she eventually turned into Kamuishu Island.

So now, when people approach Lake Mashu, the old woman is said to think she has found her grandson and sheds happy tears of rain or snow.

After enjoying the beauty of Lake Mashu along the path at the First Observation Deck, let’s check out the souvenir shop. Compared to the purely scenic Third Observation Deck, the facilities here are more complete. The entire sales area is quite enjoyable to browse. Rather than shopping, bears love visiting gift shops at scenic spots. There’s a dazzling array of things to look at and consider... ^^

The adorable Potato Chips Brothers — I’ll buy the duty-free ones at the airport instead... =^^=

Marimo tea — add hot water and the marimo expands. I also bought a marimo to raise before.

There are so many varieties and flavors of milk candies, they’re irresistible too.

Canned bear meat, sea lion meat, and venison, all miso-flavored. I felt a little cold seeing them... ^^"

The samples in Japan are really generous.

Unlike the snacks earlier, the back area is the gift section, ranging from traditional wood carvings to popular bear-themed merchandise.

There’s a whole row of cute bear-shaped ornaments on the shelf — it's so hard to decide whether to buy or not.

In addition to scenic postcards, there are also three-dimensional postcards shaped like bear paws, crabs, and more.

Lake Mashu is often shrouded in fog and is thus also known as the "Foggy Lake Mashu." As a result, the Lake Mashu fog canister has become a local specialty and can even be mailed with a stamp attached.

Also, another must-try is the Lake Mashu ice cream, which comes in four flavors: Lake Mashu Blue, Ice Tree, Fog, and a limited-time-only Rich Milk flavor. We bought the Lake Mashu Blue and Fog flavors. The bear really liked the Lake Mashu Blue—it has a subtle blue hue and tastes like a fizzy soda candy, quite refreshing and memorable. It lacks the mystery of the fog but has the deep allure of blue.

Be sure to collect the Lake Mashu commemorative stamps.

The view of Lake Mashu outside the souvenir shop.

It’s said that those who visit Lake Mashu without encountering fog may face bad omens—such as couples breaking up, businesspeople facing setbacks, or unmarried individuals experiencing delays in marriage—due to how rarely the lake is clear. On this day, the bear experienced the contradictory luck of seeing a clear Lake Mashu. Amid the serene lake, we admired the beauty of clouds reflected in the sky and mountains mirrored in the water. The sapphire-like sheen and its little dimples were unforgettable—not mysterious like in the fog, but profound in its blueness.

Lake Mashu
Phone: 015-482-1530 (First Observation Deck Souvenir Shop)
Address: Lake Mashu Plain, Teshikaga Town, Hokkaido
Business Hours: 08:00 – 18:00 (Closed from late November to early April; free parking available, but visitors assume all risk in case of accidents)

◎ Transportation Information:Please click here
◎ Hokkaido Teshikaga Town Tourism Information:Please click here

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