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Rishiri Rebun Sarobetsu NP, Hokkaido
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A local guide's route reaches Mikazuki-numa only by winter snowshoe. When nearby Otatomari-numa freezes, hikers cross its ice, then climb to the tucked-away pond.
Mikazuki sits in Numaura Maar, 2 linked explosion craters with a gourd-shaped outline, formed more than 7,000 years ago. Peat later filled much of their low floor, leaving wetlands and ponds.
The crater's history has a shoreline twist: an archaeological report links Jōmon-period seawater entering the Numaura hollow—and later sea retreat—to the formation of its wetlands and ponds.
Rishirifuji Town records Ota-tomari as an older Ainu name for the wider Numaura district, meaning “sandy inlet.” It describes the neighboring coastal landscape—not Mikazuki-numa itself.
A 2024 island beetle catalogue cites 6 diving-beetle species recorded at Mikazuki-numa, including Agabus japonicus and Acilius japonicus—tiny hunters easy to miss from shore.
Mikazuki is part of Numaura Wetland, included in the Environment Ministry's Important Wetlands listing for Rishiri. Plants here include cotton grass, Labrador tea and bog cranberry.
