Welcome to Izajima! The island in which Naka-Onsen and Mu are located.
Izajima is a small island comprised of two main provinces-- Nagi and Nami. Each province and its inhabitants are guarded by their very own mountains, aptly named Nagiyama and Namiyama. If you look closely you will find Naka-Onsen on the left, sitting just under the peak of Nagiyama.