We tried out the two private rental Onsen hot springs baths – that guests can rent for private use (貸切露天風呂) at Gosho Gekkoju (御処 月洸樹), a luxury Onsen (hot springs) ryokan with just 8 rooms total, and located in the Kurokawa Onsen area of Kumamoto Prefecture on the Southern island of Kyushu, Japan. The first is called “Dokutsuburo” (洞窟風呂 – “Cave Bath”), while the other one is Tenku-no-Yu (天空の湯), an outdoor open-air Onsen bath (貸切温泉露天風呂.)
AloJapan.com