Nanki-Shirahama Tsubaki Onsen Ryokan Shirasagi

Shirasagi is a toji (hot spring cure) inn in Tsubaki Onsen, a quiet coastal hot spring settlement in Shirahama Town, Wakayama Prefecture, about ten minutes south of central Nanki-Shirahama along Route 42. Tsubaki Onsen appears as a noted spring in the Edo-period gazetteer Kii Zoku Fudoki, and the first inn was built here in 1902, which marks the beginning of the village as a destination for cure bathing. Shirasagi itself opened in 1954 and is one of very few inns in the Kansai region that still supports self-catering cure stays.

The source, called Horai-yu, is a simple sulphur spring emerging at 31.9C. It ranks among the most strongly alkaline waters in western Japan, generally cited at pH 9.9; the inn's own site states pH 10 or above, while the Jun-Onsen Association recorded 9.8 during its inspection. The water is clear and colourless and leaves the skin noticeably slippery. Nothing is added to it and nothing is filtered or recirculated, so every tub is free-flowing, but because the source is only in the low thirties the main baths are heated continuously. The Jun-Onsen Association certifies the men's and women's main baths as Jun-Onsen C: no dilution, no recirculation, no disinfectant and no bath additives, with heating the only intervention.

Bathing areas include a view bath 60 metres above sea level looking out over the Pacific, one indoor bath for each sex, and a set of rotating herbal baths, two on the men's side and three on the women's. Those rotating tubs use mugwort, aloe, loquat leaf, mandarin, yuzu, wood vinegar, seaweed and medicinal herbs depending on the day, and are left unheated at the source temperature of 31C for a deliberately tepid soak. Day visitors are welcome from 11:00 to 20:00, or until 14:00 when the inn is full, for 700 yen per adult and 300 yen per child, with under-twos free. Parking is free for 22 cars.