Naminoyu Akane is a one-of-a-kind open-air bath built atop wave-breaking blocks along the shore of Tachibana Bay in Obama Onsen. At high tide, the water surface sits just 20 centimeters above the sea, creating the extraordinary sensation of bathing in the ocean itself. The bath operates by reservation only as a private facility for families, couples, or small groups. The sodium chloride water is drawn from Obama Onsen, which boasts the highest thermal heat emission in Japan. The experience reaches its peak at dusk, when bathers can watch the sun descend into Tachibana Bay while immersed in steaming mineral water. The sound of waves, the distant glow of fishing lights, and the vast expanse of the sea combine for an unforgettable sensory experience. A hot spring steamer is installed beside the bath, allowing guests to steam fresh seafood and vegetables using geothermal heat. The facility may close depending on weather and wave conditions.