Lake Mashu, Hokkaido | That Blue Looks Like It's Been Edited — It Hasn't

By Nihongo to Japan · Updated June 17, 2026

I sent a photo to a friend and he asked if I'd retouched it. I hadn't. That's just the color. Lake Mashu's blue is deep enough to look unreal — and being able to see it clearly at all is a matter of luck.

When I sent the photo to a friend, he asked if I'd edited it.

I hadn't. That's just the color.

/images/articles/mashu-lake-hokkaido-01.jpg

Lake Mashu's blue has its own name — 'Mashu Blue.' It's a caldera lake with no rivers flowing in or out. The water is almost entirely isolated from outside contamination, and its transparency has been measured as the clearest in the world. When sunlight enters, the blue isn't a reflection of the sky — it belongs to the lake itself.

Deep. Still. The kind that leaves you silent.

/images/articles/mashu-lake-hokkaido-02.jpg

Seeing It Is a Matter of Luck

Lake Mashu's other name is 'Kiri no Mashu-ko' — Lake Mashu in the Fog. For more than half the year the lake is buried under thick fog. Many people make the trip, see nothing, and leave.

I went in winter: clear sky, no clouds, the lake and snow-covered mountains laid out in front of me. Navigation took me to the First Observatory. The snow in the parking lot was still uncleared, the kind of cold that hits immediately.

/images/articles/mashu-lake-hokkaido-03.jpg

In the center of the lake sits a small island called Kamuisshu, meaning 'Island of the Gods' in the local Ainu language. No one can land on it. It just floats there, so still it makes the whole scene feel more unreal.

/images/articles/mashu-lake-hokkaido-04.jpg

Travel Info

Lake Mashu is in Teshikaga-cho, Hokkaido. About 1 hour by car from Kushiro. Nearby: Lake Kussharo and Mt. Io — perfect for a day trip. In winter, roads ice over; rent a car with four-wheel drive or winter tires.

Book Hokkaido transport and experiences on Klook:

https://klook.tpx.lv/IuSKdjjt