Odakyu Hotel Hatsuhana

Every room here has its own open-air onsen bath on the terrace. The hotel also has two shared bathhouses on the first and second floors, Takenoha (竹の葉) and Yamanoha (山の端), that swap between men and women through the day; the second-floor one has a sauna. There are also four baths you can reserve for a private soak. Kawatonoyu (川音の湯), the only outdoor one, sits right along the Sukumogawa river with a square, infinity-edged tub, a lie-down pool and a deeper soak. The three indoor ones each have their own mood: an octagonal tub under a high, beamed ceiling, a bath that seems to spill into the pond outside its window, and a round one lit by fiber-optic light in a stone garden. In summer a couple of the tubs are kept closer to body temperature for longer, easier soaks. The spring water itself is clear and alkaline, soft on the skin. Hatsuhana is a ryokan-style hotel tucked into the Oku-Yumoto stretch of Hakone-Yumoto onsen, above the Sukumogawa river, reopened after a 2022 renovation. It's quiet and refined, built around long baths and kaiseki dinners rather than a day trip: a top-floor terrace looks out over Mount Yusaka, but bathing here is for overnight guests only.