This was finally the last facility. If I could, I would stay for months and visit every hot spring and sauna facility across the Kanto region. But that's not realistic—I have to return home. That's why I thoroughly research in advance so I can make the most of the limited time I have. During that research, I found a facility that uses free-flowing source hot spring water for all tubs (including the cold plunge bath) and has two saunas. Digging deeper, it seemed to be one of the top facilities in Kanagawa Prefecture. The facility is called Asahiyu Gensen Yuiru. I arrived about 10 minutes by taxi from Keikyu Kawasaki Station. It sits along the road with a subtle presence—you could easily pass it without noticing. I had expected an ordinary super sento, but the 2-hour course costs 2,480 yen, which is a respectable price. I hoped the hot spring, saunas, and cold plunge bath would be worth it. After changing, I entered the large bath area and found it to be very compact. It felt smaller than in photos, more like a neighborhood sento in scale. However, the natural hot spring pouring into the tubs was a rare, genuine hot spring. They struck hot water after drilling 1,200m underground, and the spring contains about 25 times the components of the standard hot spring benchmark, earning it a designation as a therapeutic spring. Japan has a culture called toji—bathing in hot springs to heal illnesses—but not every hot spring improves health. Only springs with overwhelmingly high component levels designated as therapeutic springs can show such effects. When I actually submerged, the water felt like it melted into my skin—an almost lotion-like texture that made me feel as if I had stepped into a luxurious bath oil. The hot spring wrapped my body and gave me supreme relaxation. This hot spring is also referred to as Netsu no Yu, and just a few minutes in was enough to warm my entire body. My prior research suggested that the cold plunge bath also uses this spring water, so I felt a surge of dopamine wondering what kind of sensation awaited. I have experienced many natural hot springs, but Asahiyu Gensen Yuiru's spring is top-class. After warming up in the hot spring, it was sauna time. Asahiyu Gensen Yuiru has two saunas: 1. Löyly sauna: A sauna room with a temperature exceeding 100℃. Automatic löyly pours a considerable amount of water onto the sauna stones at regular intervals, filling the room with intense waves of heat. 2. Aufguss sauna: A spacious sauna room set at 85℃, specialized for aufguss. Events are held every hour. When there are few guests, you can even enjoy the sauna while lying down. I started with the löyly sauna as a greeting. With the room over 100℃, it was extremely hot. However, the steam from the löyly raises the humidity, so it doesn't feel like needles on the skin. The space is designed for a comfortable sauna experience. There is no TV, and it's a quiet room suitable for meditation. After warming up for a while and reaching my limit, I headed to the cold plunge bath. The cold plunge bath was lavishly filled with the same remarkable hot spring water that had impressed me earlier. After rinsing off sweat, the spring water wrapped around me again with that melting sensation. In terms of smoothness, this water might be the best I've ever encountered in my life. It was that soft. The water temperature is 13℃, quite cold, but because of the extraordinary silkiness it doesn't feel piercing on the skin and is deeply pleasant. It is the most delightful cold plunge bath. After the cold plunge, I rested in a dedicated relaxation area. I could think of nothing due to the overwhelming comfort. If you want to experience an outstanding cold plunge bath, this facility is a must-visit. For the second set, I enjoyed the aufguss sauna. The aufguss event was about to start, so I joined. The format was music playing while the heat master performed towel theatrics. The heat master waved the towel in time with the music for over ten minutes, and by the end his shoulders could barely lift. Guests cheered spontaneously. The event finished with many guests praising the performance. I quietly expressed my thanks in a barely audible voice. After the aufguss, I plunged back into the sublime cold plunge bath. What makes Asahiyu Gensen Yuiru's cold plunge bath so wonderful is not only that it uses hot spring water. The designers deliberately made the bath deep enough to submerge fully, so you can immerse your head to your toes in the exquisite spring water. There is nothing more pleasant than a deep, wide cold plunge bath—and since they use an exceptionally powerful hot spring, it's no wonder this place ranks among Kanagawa's most popular facilities. While resting in the relaxation area, I completely lost consciousness. I don't know how long I slept, but when I came to I decided to enter the sauna for a third set. For the third set, I returned to the löyly sauna. I wanted to experience an intense löyly. I deliberately sat on the top bench and waited for the löyly to begin. The room lights changed and the löyly started. An incredible amount of water was poured onto the sauna stones—as if buckets of water were dumped at once. In an instant, a ferocious wave of heat swept the room. It felt as if my face and ears were burning; the pain was intense. Breathing became difficult and I panicked. I immediately moved from the top bench to the lower bench to escape the emergency. Even on the lower bench, it was still searing. I had never experienced such a fierce löyly. Looking back at the top bench where I had been sitting, there was a person who had been beside me from the start, arms folded, eyes closed, radiating a samurai-like aura. Even amid that heat wave he barely moved, enduring the intense heat while maintaining a rigid posture. What strength. I didn't know who he was, but I felt awe and left the sauna before him. I once again entered the sublime cold plunge bath, and with that my sauna day was complete.

Asahiyu Gensen Yuiru also serves delicious food. Their original spice curry is exceptional—I ordered it myself. The flavor is superb; the unique spice blend stimulated me from the inside and made me sweat profusely. It made me feel like I needed another dip in the cold plunge bath. After the meal, I rested for a while and reflected on this sauna trip. I had planned this trip more than two months in advance and approached it with serious enthusiasm. I flew into Tokyo on a night flight, then spent 3 nights and 4 days visiting a total of 7 facilities. I feel I had excellent experiences at each one. I was also able to meet a colleague I respect. In addition to the sauna journey, having time to meet people made this trip very meaningful. Indeed, the Kanto region has many wonderful facilities. There are still countless places I want to visit. Living in Kanto would make travel easier, but I won't do that—shorter travel distances reduce the sense of journey. Using planes and trains every time and traveling long distances is how I experience the extraordinary; returning home I can restart life with a new perspective. That's part of the appeal of travel: experiencing things you haven't experienced and sensing things you've never seen. Sauna trips are full of stimulation, and I want to continue pursuing that stimulation. With that, this sauna trip comes to an end.