Mix hot spring water into the cold plunge bath. From the moment I heard that idea, I couldn't think of anything else. They draw up natural underground water and add hot spring source water to it. No chiller is used. No circulation. A continuous feed at 14–16°C. From those conditions alone you can imagine how unbelievably pleasant the cold plunge bath must be. I have thoroughly experienced how good a continuously fed natural-water cold plunge bath without a chiller can feel on my travels. Now add the silky quality of onsen water on top of that. What on earth would that feel like? Just the thought made me tremble. In the morning I was moved by an excellent sauna and architecture at Fujiyama Onsen, and after bathing I saw the full view of Mount Fuji for the first time. From there I cycled around Lake Kawaguchi, soaking in Fuji's spectacular views until sunset. After returning the rental bike, I boarded the Fujikyuko Line. The night's sauna trip was beginning. Tsuru-shi Station was unmanned. When I exited the ticket gate, it was dark and there was no sign of people. It felt so deserted that I wondered if a representative Yamanashi onsen facility could really be here. But after a few minutes' walk the building I had seen in photos appeared. Many cars were parked in the lot. I took an exterior photo and entered the facility. Contrary to the quiet station, the inside of the facility was bustling. Families, groups of friends, solo visitors—various people came and went, and the place was lively. I think there are two kinds of facilities. One offers a quiet space for personal maintenance. The other is like a community where families and friends can have fun loudly while solo visitors can still enjoy themselves. Yamanashi Tomareru Onsen Yorimichi no Yu was clearly the latter. The liveliness felt pleasant. After completing check-in, I headed to the large public bath. The indoor baths were, to be honest, like a typical super sento and not particularly special. But what caught my eye was the continuously fed cold plunge bath. Indeed, water was flowing in steadily. It was placed immediately outside the sauna room so you can exit the sauna and step right into the water. Perfect. Moving to the outdoor area, the atmosphere changed completely. A large rock bath with continuously fed hot spring water sat proudly. I would enjoy that later. I cleansed myself and warmed up in the indoor carbonated bath, then headed to the sauna. First set. The moment I sat on the top bench in the sauna, an automatic löyly started. Perfect timing. A large amount of water was poured onto the sauna stones, and seconds later an intense wave of heat enveloped the room. A Metos isness stove was in use; its design fuses gas far-infrared heat with sauna stones so it warms you from the core. Perhaps because of that, the whole sauna was filled with heat and humidity. The automatic löyly was too hot, so I instinctively moved down one level. At the same time, the man sitting next to me also moved down. Our eyes met. "It's really hot, isn't it…" I couldn't help but say with a laugh. He laughed too. Those small exchanges are part of the joy of sauna. I soaked in the heat, letting my body warm slowly. It was a wonderful sauna to cap off the day. I decided to go all out. Finally, the moment I had been waiting for: the cold plunge bath. I rinsed off my sweat and slowly immersed myself. The perceived temperature was 14°C. Cold. But something else was mixed into that cold. Alongside the softness of the underground water there was the silky texture of hot spring water on the skin. The Fujiyama Onsen's natural Fuji water I encountered last night at Hotel Mount Fuji and earlier that morning had a crisp, refreshing quality. This cold plunge here was a little different. It was mellow and, though the expression may sound odd, it had a texture that made me feel a hint of warmth even though it was a cold plunge. It was so pleasurable I almost forgot it was a cold plunge. I moved to the outdoor area, leaned back in a chair, and looked up at the night sky. The Yamanashi night breeze gently caressed the body cooled by the cold plunge. I felt the little hairs on my arms standing up. I never expected to end the day with an experience like that. Second set. Still feeling the afterglow of the outdoor cool-down, I first soaked in the outdoor natural hot spring. Hot spring water gushed energetically into the continuously fed rock bath. Immersing in the natural onsen after an exquisite cold plunge and outdoor cool-down is a classic routine at facilities with great hot springs. I realized then how well thought-out the rock bath's design was. The backrest has an angle that lets you soak in a relaxed posture. Many facilities use a right angle, but a right-angle backrest can strain your neck when you try to lean back and float, making it hard to maintain for long. Also, there are spots on the rock bath where you can rest your head. You can lie back and bathe. It felt as if the designers imagined how bathers move. These small considerations greatly affect the quality of the experience. After slowly warming up again I returned to the sauna. The isness stove's heat wrapped around me once more, and I plunged into the cold plunge. Even on the second round, the impression did not fade. I was enveloped again by the unique mellow quality that comes from mixing underground water with hot spring source. When I collapsed into the outdoor relaxation chair, I was so dazed I couldn't move for a while. Third set. I decided to join an aufguss event. A staff member entered the sauna. It was a quiet aufguss. After pouring aromatic water onto the sauna stones, they fanned the room without speaking—steadily and calmly. It wasn't a flashy performance, just a simple routine. They gave each person three waves of heat, and in a sauna that had been hot even with automatic löyly, an aufguss made it even hotter. The intensity was a fitting end to the day. I left the room partway through. I usually exit partway when I join an aufguss because if I stay until the end the cold plunge becomes extremely crowded. To have a great experience, sometimes you need to move differently from the crowd. If you leave midway, you can fully enjoy the cold plunge. I feel a little guilty toward the staff, so I always say "Thank you" when I leave. That way I don't feel bad. I finished with the exquisite cold plunge bath, and that ended my sauna activities for the day.

I dined at the facility's restaurant. I hesitated over what to order but chose yurinchi. The instant I bit into the served yurinchi I widened my eyes. It's delicious. Truly delicious. The crispy fried chicken coated in a sweet-spicy sauce soaked into my body tired from the sauna. The perfect meal to end an incredible day. There was nothing left to do; I would sleep soundly and prepare for a new journey tomorrow. After leaving the facility I traveled from Tsuru-shi Station to Otsuki Station and checked into a business hotel. That day was my last in Yamanashi. This trip, which began at Sauna Shikiji, saw me miss a view of Fuji at Hotel Mount Fuji, encounter sublime architecture and vanadium-rich water at Fujiyama Onsen, finally achieve the long-awaited scenic view at Lake Kawaguchi, and be enveloped by a cold plunge where natural underground water meets onsen source at Yamanashi Tomareru Onsen Yorimichi no Yu. The water in Yamanashi was exquisite everywhere. From tomorrow I would head to Nagano. I would travel to Chino City in Nagano Prefecture and then to Shirakaba Resort Ikenotaira Hotel Koten no Yu at Lake Shirakaba, a facility where you can sauna while overlooking Lake Shirakaba.