Hachikurō Onsen (八九郎温泉) is an onsen located in Kosaka. The onsen was constructed by the local community and the water used here is the same as in Okuhachikurō Onsen and Okuokuhachikurō Onsen. It is housed in what looks like a plastic greenhouse. Unlike Okuhachikurō and Okuokuhachikurō the baths here are separated. It is completely free to use.