Hiruzen Royal Hotel — Highland Onsen

Hiruzen Royal Hotel's Highland Onsen sits on the Hiruzen Highland plateau in Maniwa city, a rural upland area in northern Okayama known for grasslands, dairy farming, and cooler mountain air than the rest of the prefecture. The bathing facility is a hotel onsen rather than a standalone bathhouse, drawing on a sodium chloride hot spring valued for its warming, salt-rich water. Its signature feature is the open-air rotenburo, which looks out over the highland's rolling terrain and distant peaks, offering a markedly different setting from the river- and forest-edge baths found elsewhere in Okayama's onsen towns. An indoor bath, sauna, and a relaxation lounge overlooking the highland views round out the facilities; there is no separate treatment menu or trained massage therapist on site, so the experience centers entirely on the bath itself rather than spa treatments. Day-use bathing runs from late morning into mid-afternoon, while overnight guests have access in the evening and again in the morning, consistent with typical Japanese ryokan-style bathing hours. Overnight stays include meals and are the more common way to experience the property, given the highland's distance from central Okayama and its appeal as a base for hiking and sightseeing on the plateau. The overall mood is relaxed and unhurried, suited to visitors seeking mountain scenery alongside a traditional hot-spring soak.