The area around Lake Onuma has been protected as a Hokkaido prefectural park since 1903, and park facilities have been developed, making it one of the oldest natural parks in Japan. On April 17, 1915, it was selected as one of the New Three Most Viewed Places of Japan, along with Miho no Matsubara (Shizuoka Prefecture) and Yabakei (Oita Prefecture), and in 1957, with support from various quarters for Lake Onuma to be elevated to a quasi-national park, a petition was submitted to the Hokkaido government. In July of the following year, 1958, Lake Onuma was designated as the 13th quasi-national park, and Lake Onuma and Mt. Komagatake became special national protected areas.

There are 126 islands of various sizes floating on Lake Onuma and the other three lakes, adding a delicate touch of color to the landscape of Lake Onuma. Some of these islands are connected by arched bridges, and you can enjoy island hopping on foot from the park plaza. On the surface of the lake, which forms an inlet surrounded by islands, you can spot water plants such as water lilies, and carp and crucian carp jumping up and down, swaying their leaves. If you're lucky, you might even see kingfishers flying over the water, or squirrels busily munching on nuts.

In autumn, the lakeside areas of Lake Onuma, Lake Konuma, and Junsai Numa take on vivid colors in Onuma Quasi-National Park. The brilliant crimson colored lakes and the distinct ridgeline of Mount Komagatake vividly display the beauty of nature. There are various ways to view the autumn leaves, such as cycling around the road, going out on the lake by canoe or boat, or climbing Mount Higurashi (303m above sea level) located to the west of the park, which offers a view of the lakeside area. Each way offers a different spectacular view.

You can fish for smelt during the winter. You can do it from a pier in December before the lake freezes over, and on the ice from early January to mid-March. There are many facilities where you can go empty-handed, so please give it a try. *Depending on the facility, you can have the smelt you catch fried for an additional fee.