Mt. Iou/Io/Iwo (Io-zan), which is referred to as Atosanupuri (naked mountain) in Ainu, rises 512 m above sea level. This active volcano emits a great deal of smoke. The lava dome where solidified lava was upheaved is believed to have been created approximately 1,700 years ago, a relatively short history for a volcano. In the vicinity lies Tsutsujigahara, where white flowers of Ledum palustre L. spp. diversipilosum can be enjoyed in early July.
The eastern part of Akan National Park contains Lake Onneto, Lake Akan, Lake Mashu, Lake Kussharo, Mt. Iou/Io/Iwo (Io-zan) and centrally located Kawayu Onsen. Once the site of a sulfur-mining operation, Mt. Io boasts over 1,500 large and small volcanic craters. Kawayu Onsen is a hot spring resort area whose waters originate in Mt. Io. A river of hot spring water (“Yu-no-Kawa”) flows through a district consisting of rows of hot spring hotels and souvenir shops.
Mt. Iou/Io/Iwo (Io-zan) Mashu National Hwy, Atosanupuri Genya, Teshikaga Town (Teshikaga-cho), Kawakami-gun, Hokkaido Prefecture 088-3463, Japan Access: Approx. 20 mins by car from JR Mashu station Contact – Teshikaga Local Village Hall, Citizens Division