The Brother Volcano of Mount Bandai: Lake Oguni, a Caldera Lake of Nekoma Volcano, and Its Surrounding Outer Rim Mountains
Nekoma Volcano, located to the west of Bandai Volcano, was formed between one million and 400,000 years ago through andesitic volcanic activity, similar to that of Mount Bandai.
Lake Oguni is a caldera lake that was created when the crater of Nekoma Volcano collapsed due to volcanic eruptions. It is encircled by the outer rim mountains, including Mount Nekoma and Mount Oguni. In early summer, vast colonies of Nikkō-kisuge (Daylilies) bloom in full splendor, and the wetland plant community of Lake Oguni has been designated a National Natural Monument of Japan.