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Akan-Mashū NP, Hokkaido
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A rooftop live camera at Mashu Kamui Terrace logged a dawn cloud sea on 23.3% of June 2025 days, 12.9% in July and 3.2% in August; it recorded none from October through March. These are the operator’s monthly camera-based rates.
From the high rim at the Third Observatory, a lucky dawn can reveal cloud seas over both Lake Mashu and neighboring Lake Kussharo. Locally, the twin display is called “double unkai”—two volcanic calderas wearing one white blanket.
Kawayu Visitor Center traces some of Mashu’s cloud-sea fog to sea fog formed off Kushiro and carried inland by southerly winds. The caldera walls help trap it, turning low-level mist into a panorama seen from above.
A fog bank can sometimes pour over the caldera rim near the First Observatory like a white waterfall. This fast-moving “taki-giri” (waterfall fog) is a rare sight, reported only a few times in summer.
The 1966 hit “Kiri no Mashuko” helped make Mashu famous for fog, though singer Akira Fuse had never visited the lake when he sang it, imagining the scene instead. The song helped make the mist itself part of the attraction.
