After enjoying alternating hot and cold baths and the binchotan charcoal sauna at Aridagawa Onsen Hikari no Yu, I stepped outside — and it was still only 10 in the morning. I'll just go have a look. That's what I told myself as I drove off, but this is something that happens to me all the time: before I know it, I'm standing at the front desk paying the entry fee. I have never once managed to just look. Driving up a narrow mountain road from Arida City, I spotted the signboard for Ninomaru Onsen along the way. A little further along, a distinctive log house appeared through the trees. The parking lot was fairly empty, so it seemed like it wouldn't be too crowded. The moment I stepped out of the car, the sound of a waterfall rushed into my ears. Right in front of me, the clear waters of the Yamada River flowed past, and the sounds of nature echoed throughout the entire facility. I stood there for a while, breathing in the crisp air and listening to the waterfall. Natural sounds alone have a way of bringing deep comfort to the human soul. Then, from the direction of the waterfall, came a burst of lively voices. It turns out that Ninomaru Onsen also has an outdoor sauna — a bold setup where you heat up in a wood-fired sauna hut called the Taki no Sauna Goya (Waterfall Sauna Cabin) and then leap straight into the plunge pool at the base of the waterfall. Those voices were almost certainly the shouts of people jumping in. I was here for the main bathhouse this time, but I'd love to try the private sauna if I get the chance. The facility is spread across three floors: the main bath on the first floor, reception, coin lockers, and the restaurant on the second floor, and a relaxation lounge on the third. I checked in, headed down to the first floor, got changed, and stepped into the main bath. It's a simple hot spring with just a single bathtub. An alkaline simple spring at pH 10.0, the kind that leaves your skin feeling silky smooth. Surely there's more to it than this? — And indeed there is. Down an outdoor staircase to the basement level, a raw concrete space opens up to reveal a sauna, a cold plunge bath, and an outdoor relaxation area. Forest stretches out ahead of you. The sound of the waterfall is always there. It's a space that makes you feel genuinely immersed in nature. The sauna is Finnish-style, with a powerful heat of 100°C bearing down on you. The cold plunge bath, I learned, uses spring water chilled by a cooler to 15°C — so you can expect the soft, gentle feel that only natural spring water can offer. Given the size of the facility, though, I doubted it could handle large crowds. Coming during a quieter time of day would definitely be the way to go. First set. I stepped into the Finnish sauna. The powerful heat of 100°C enveloped my entire body. The warmth spread thoroughly through the three-tiered interior. The scent inside the sauna room was pleasant — a different kind of heat from the binchotan charcoal sauna at Hikari no Yu earlier, with its own distinct texture. I warmed my body slowly and thoroughly, then headed to the cold plunge. I sank my whole body into the 15°C cold plunge bath, chilled from natural spring water. It fits around five people, and sure enough, the spring water is soft. There are no sharp edges like tap water — there's a certain gentleness within the cold. Having already experienced the Aridagawa underground stream cold plunge at Hikari no Yu earlier, today had turned into a wonderfully indulgent day of natural water through and through. In the outdoor relaxation area, the forest spread out before me. I settled into a chair, breathed in the clean air deeply, and took in the natural sounds around me. The waterfall. Birdsong. The wind rustling through the trees. This is the kind of outdoor relaxation you simply can't get at a super sento. I sat there for a while, gazing peacefully at the scenery. For my second set, I followed the same flow — sauna, cold plunge, outdoor relaxation. Since this was my second stop of the day, two sets was plenty. My body was completely, perfectly done.

After enjoying alternating hot and cold baths and the binchotan charcoal sauna at Aridagawa Onsen Hikari no Yu, I stepped outside — and it was still only 10 in the morning. I'll just go have a look. That's what I told myself as I drove off, but this is something that happens to me all the time: before I know it, I'm standing at the front desk paying the entry fee. I have never once managed to just look. Driving up a narrow mountain road from Arida City, I spotted the signboard for Ninomaru Onsen along the way. A little further along, a distinctive log house appeared through the trees. The parking lot was fairly empty, so it seemed like it wouldn't be too crowded. The moment I stepped out of the car, the sound of a waterfall rushed into my ears. Right in front of me, the clear waters of the Yamada River flowed past, and the sounds of nature echoed throughout the entire facility. I stood there for a while, breathing in the crisp air and listening to the waterfall. Natural sounds alone have a way of bringing deep comfort to the human soul. Then, from the direction of the waterfall, came a burst of lively voices. It turns out that Ninomaru Onsen also has an outdoor sauna — a bold setup where you heat up in a wood-fired sauna hut called the Taki no Sauna Goya (Waterfall Sauna Cabin) and then leap straight into the plunge pool at the base of the waterfall. Those voices were almost certainly the shouts of people jumping in. I was here for the main bathhouse this time, but I'd love to try the private sauna if I get the chance. The facility is spread across three floors: the main bath on the first floor, reception, coin lockers, and the restaurant on the second floor, and a relaxation lounge on the third. I checked in, headed down to the first floor, got changed, and stepped into the main bath. It's a simple hot spring with just a single bathtub. An alkaline simple spring at pH 10.0, the kind that leaves your skin feeling silky smooth. Surely there's more to it than this? — And indeed there is. Down an outdoor staircase to the basement level, a raw concrete space opens up to reveal a sauna, a cold plunge bath, and an outdoor relaxation area. Forest stretches out ahead of you. The sound of the waterfall is always there. It's a space that makes you feel genuinely immersed in nature. The sauna is Finnish-style, with a powerful heat of 100°C bearing down on you. The cold plunge bath, I learned, uses spring water chilled by a cooler to 15°C — so you can expect the soft, gentle feel that only natural spring water can offer. Given the size of the facility, though, I doubted it could handle large crowds. Coming during a quieter time of day would definitely be the way to go. First set. I stepped into the Finnish sauna. The powerful heat of 100°C enveloped my entire body. The warmth spread thoroughly through the three-tiered interior. The scent inside the sauna room was pleasant — a different kind of heat from the binchotan charcoal sauna at Hikari no Yu earlier, with its own distinct texture. I warmed my body slowly and thoroughly, then headed to the cold plunge. I sank my whole body into the 15°C cold plunge bath, chilled from natural spring water. It fits around five people, and sure enough, the spring water is soft. There are no sharp edges like tap water — there's a certain gentleness within the cold. Having already experienced the Aridagawa underground stream cold plunge at Hikari no Yu earlier, today had turned into a wonderfully indulgent day of natural water through and through. In the outdoor relaxation area, the forest spread out before me. I settled into a chair, breathed in the clean air deeply, and took in the natural sounds around me. The waterfall. Birdsong. The wind rustling through the trees. This is the kind of outdoor relaxation you simply can't get at a super sento. I sat there for a while, gazing peacefully at the scenery. For my second set, I followed the same flow — sauna, cold plunge, outdoor relaxation. Since this was my second stop of the day, two sets was plenty. My body was completely, perfectly done.