A trip that goes exactly as planned is a boring trip. I jumped on the Shinkansen without even booking a place to stay, drifting wherever the wind took me, hopping from sauna to sauna. That free-spirited, wandering journey had finally reached its last day. Just because it was the last day didn't mean I was going to coast through it with nothing but travel. Making the most of hot springs and saunas right up to the final moment — that's my way. I had already decided where to go in the morning: Tsunashima Gensen Yukemuri no Sato in Yokohama. I'd had my eye on the place for a while after hearing rumors of an exceptional cold plunge bath made with natural black spring water. I checked out of the APA Hotel in Minatomirai where I'd spent the night, boarded the Toyoko Line, and headed to Tsunashima Station. From there, a shuttle bus carried me to the facility. Looking up, I saw a massive noren curtain emblazoned with "Yukemuri no Sato" swaying in the breeze. It felt less like a super sento and more like a high-end hot spring inn. The quality and scale of the place had my heart racing before I'd even stepped inside. Once inside, the space that spread before me far exceeded my mental image of your typical super sento — refined and uncompromising in every detail, from the lounge and restaurant to the rock spa area. Even the scent was wonderful. I headed straight for the main event: the large communal bath. The locker room was spacious and very comfortable. I'd timed my arrival to catch opening on a weekday at 9 a.m., so there were few other guests — perfect conditions. The moment I stepped into the bathing area, the chic, dark-black stonework aesthetic completely captivated me. A magnificent bonsai was placed at the center of the space, blending Japanese sensibility with modernism. Immediately to the left of the entrance was the Finnish sauna, and right next to it was my target: the black spring water cold plunge bath. I glanced at the thermometer. It read 9°C. Single digits. They were chilling natural amber-colored hot spring water all the way down to single digits — what kind of brutal, or rather, supremely blissful sensation was waiting for me? Stepping out into the outdoor area only deepened the atmosphere. Just being in that lush, Japanese-garden-style space was enough to feel the stiffness built up from daily life beginning to melt away. Into the rock-hewn tub, amber hot spring water the color of black coffee flowed in an endless stream. Beside it was a 22°C natural spring overflow bath, which could easily serve as a milder cold plunge. And at the far end, I spotted a salt sauna. A perfect lineup. After surveying the full facility, I cleansed myself and soaked in the open-air natural spring. In Tokyo and Kanagawa, it's not too hard to find places with this kind of amber black water, but back in the Kansai region you rarely come across it — so for me, this was a genuinely precious experience. Soaking in the smooth, slightly viscous water, I felt the tension from the long trip slowly dissolving from deep within my body. The perfect warm-up complete, I headed at last to the Finnish sauna. The moment I opened the sauna door, intense heat struck my face. The thermometer read over 100°C. The massive rocky sauna stove was piled high with what seemed like an extravagant amount of sauna stones, and self-service löyly was available. There was a TV in the room, but the volume was completely off. That, I thought, is genuinely wonderful. I prefer saunas where I can face myself in silence. When I want to truly concentrate, the noise of a variety show on TV is nothing but a distraction. Only a facility that takes quality sauna experiences seriously would choose to keep it quiet. Sitting there listening to nothing but my own heartbeat in the stillness, another guest sharing the sauna poured water for a löyly. The sauna stones let out a satisfying sizzle, and hot steam surged through the 100°C space. It was intense heat, but knowing that single-digit cold plunge was waiting for me afterward gave me a strange surge of willpower to hold on to my absolute limit. I pushed my body to the point where I couldn't take any more, then left the sauna. I rinsed off and sank into the cold plunge — natural spring water chilled to 9°C, tinted that deep amber. The instant I entered the water, every pore across my body cried out and snapped shut all at once. An intense cold shot straight through to the top of my skull. But it wasn't just cold. The soft, velvety quality unique to black spring water gently enveloped my skin, and beneath the cold there was an unmistakable, genuine sense of relaxation. It felt absolutely incredible. I hauled myself out of the cold plunge and moved directly into an outdoor air bath. Thanks to the perfectly designed flow of the space, I was able to collapse into a chair without a single wasted step. The crisp morning air, the green of the trees, and the blood surging through every inch of my body. I savored that early-morning totonou to the fullest. For the second set, I headed to the salt sauna in the outdoor area. It's a compact space for about eight people, but the temperature is around 80°C — quite high for a salt sauna. This one also had an auto-löyly system in the Finnish style, so the heat hit immediately upon entering. When I felt the sweat starting to build up, I rubbed a generous amount of salt all over my body. Minerals seeped into my skin. Applying the salt sent the perceived temperature shooting upward, and the sweating was stimulated at a remarkable speed. After the salt sauna, I moved to the outdoor natural spring overflow cold plunge. The water temperature was around 23°C — flowing straight from the source at its natural temperature. The brutal, electrifying rush of the single-digit plunge is extraordinary in its own right, but there's something equally wonderful about surrendering yourself for a long time to a naturally mild cold plunge like this. I simply savored the softness of the water as I felt my body slowly cooling down. After going deep into totonou again with another outdoor air bath, the third set brought me back to the Finnish sauna. I scorched my body thoroughly with the 100°C-plus heat, then snapped back to life with the 9°C single-digit black spring water cold plunge. It was a perfect morning sauna session.

After thoroughly enjoying the sauna, I decided to have lunch at the restaurant inside the facility. As I brought delicious food to my mouth, I let my mind wander over plans for what was next. It was still before noon. I was planning to take the Shinkansen back to Osaka in the evening, but there was plenty of time left. "Never let the spirit of exploration fade, right up to the last moment of a trip." That's my belief. I could have headed home from here, but surely there was at least one more wonderful place out there waiting for me. I picked one facility from the shortlist I had stored in my head — a brand-new spot in Oimachi, Tokyo. It had been on my mind throughout the past few days. All right, that settles it. I gathered my things and left Yukemuri no Sato, not without a twinge of reluctance. The next destination: Sauna Metsä Oimachi Tracks. The journey wasn't over yet.