The area around Onuma has been protected as a Hokkaido prefectural park since 1903, with park facilities being developed, making it one of the oldest natural parks in Japan. On April 17, 1915, it was selected as one of the New Three Views of Japan, along with Miho no Matsubara (Shizuoka Prefecture) and Yabakei (Oita Prefecture). In 1957, supported by a movement from various quarters to upgrade Onuma to a quasi-national park, a formal request was submitted to the prefecture. In July of the following year, 1958, Onuma Prefectural Park was designated as the 13th quasi-national park, and Onuma and Mount Komagatake became national special protection areas.

In the three lakes, including Lake Onuma, there are 126 large and small islands, adding a delicate touch of color to the scenery of Onuma. Several of these islands are connected by arched bridges, allowing visitors to enjoy island hopping on foot from the park plaza. On the surface of the lake, which forms coves surrounded by islands, you should be able to spot aquatic plants like water lilies, as well as carp and crucian carp leaping and rustling the leaves. If you are lucky, you might also see kingfishers flying over the water's surface or squirrels busily nibbling on nuts.

In autumn at Onuma Quasi-National Park, the entire lakeside area of Lake Onuma, Lake Konuma, and Junsai Numa turns vibrant colors. The lake, colored in vivid crimson, and Mount Komagatake with its distinct ridgeline, vividly display the beauty of nature. There are various ways to enjoy the autumn foliage, such as cycling on the road that circles the lake, going out on the lake in a canoe or boat, or climbing Mount Higurashi (elevation 303m), located to the west of the park, which offers a panoramic view of the lakeside area. You can enjoy spectacular views, each with a different aspect.

During the winter, you can enjoy smelt fishing. In December, before the lake freezes over, you can fish from the pier, and from early January to mid-March, you can fish on the ice. There are many facilities where you can go empty-handed and enjoy the experience, so please give it a try. *Depending on the facility, the smelt you catch can be deep-fried for an additional fee.