Mt. Toyonidake (1,105 m) is a fine-shaped mountain located in the southern end of the Hidaka Mountain Range. As is shown by its name “Toyoni” meaning “a place with a pond” in the Ainu language, Lake Toyoni lies at the foot of the mountain. Seen from Erimo Town, Mt. Toyonidake is behind Mt. Okishimappu; thereby the mountain is also called “Nimaidake,” which means the mountain seen behind. The mountainside is bristled with Erman’s birch trees and Siberian Dwarf Pine trees. As is the case with other mountains of Hidaka, the ridge is narrow and precipitous.

From the top of the mountain, you can command a fine view of the coastlines on both sides of Cape Erimo in front, while in your back is an exquisite view of Hidaka mountains, which are overlapping with one another. Herd of Ezo deer can be observed in the mountain. However, climbers must be careful because game hunting of Ezo deer is open in winter.