Shiosai no Yu is a day-use hot spring facility attached to Marin Terrace Ashiya, a National Lodging House in Ashiya Town, Ongagun. From the large public bath, you can enjoy an open view of the sea in Ashiya with light streaming in, and the observation open-air bath offers two types that alternate daily: a rock bath and a Mikage stone bath. The sauna comes in two varieties, mist and Mikage stone, also offered on a rotating daily basis, and a cold plunge bath is available as well. Enjoy the set of sauna and cold plunge bath, or outdoor air bathing in the open air bath area, while taking in the sound of the seaside surf.