Mount Komagatake, the park's centerpiece, experienced a major eruption in 1640 that permanently reshaped the regional topography.
The park contains 126 small islands across Onuma and Konuma lakes.
Junsai, a type of edible water shield plant, is harvested from the lake and serves as a local culinary specialty.
The park was designated as a Quasi-National Park in 1958, the first in Hokkaido.
The area is a transit point for over 100 species of migratory birds, including the whooper swan.
The volcanic soil has led to a distinctive botanical composition, including dense groves of Japanese white birch.
Onuma Quasi-National Park is defined by the symmetrical profile of the active-turned-dormant volcano Mount Komagatake, which towers over a series of caldera lakes. The park encompasses Onuma, Konuma, and Junsai lakes, characterized by numerous small, wooded islands linked by a network of bridges. The landscape was significantly altered by the 1640 eruption of Mount Komagatake, which blocked river flow and created the current lake configuration. Visitors can navigate the park via interconnected walking trails, including the 15-minute and 50-minute island loop courses. The area is a protected habitat for migratory birds, particularly whooper swans during the winter months. Aquatic activities like pleasure cruises and pedal boats operate on the lakes during the warmer seasons. In winter, the lake surface freezes, allowing for ice fishing and snowshoeing excursions. The park acts as a key site for observing the unique juxtaposition of volcanic geology and lush wetlands in southern Hokkaido.
The red bridge (Getsudebashi) providing a direct frame for Mount Komagatake.
Rent a bicycle near the station to cover the perimeter road, which offers expansive views inaccessible by foot.
Bring mosquito repellent during the summer months, as the wetlands attract significant insect activity.
Visit the dedicated observation decks early in the morning to capture the clearest reflection of Mount Komagatake on the lake water.
Do not attempt to hike the upper slopes of Mount Komagatake without checking current volcanic alert levels and local access restrictions.
Pleasure cruise boat services are suspended during the winter freeze; certain hiking trails may close during heavy snow accumulation.
Stay on marked wooden boardwalks to protect the delicate wetland ecosystem; do not feed wild waterfowl.
