The Kushigamine mountain is located in the southern Hakkōda Mountains and it is exactly the place where the Aoni stream originates. The clean and sweet water flows down the Kushigamine mountain, with more and more water running in, the Aoni stream flows through the old-growth forest. Somewhere it would flow very quickly and somewhere it turns into a fall. Surrounded by mountains, the Aoni Onsen is spared from the bustling world outside. It is also widely known as the ""lanterns-illuminated Onsen"" across Japan. The ""Kenroku-no-yu'' (Hot Spring) is built with Hinoki cypress and includes a gender-separated inner bath, a female-only sauna house, a rock bath, and 2 open-air hot springs.