Friday night: clocked out at 6 p.m., boarded a 8 p.m. flight, touched down at Haneda Airport at 9:30 p.m. A perfectly smooth sequence — sauna, cold plunge, outdoor rest — but make it a travel itinerary. I made my way from Haneda to Oimachi Station, and despite it being close to 10 p.m., the trains were absolutely packed. For someone like me who's been living a quiet, semi-retired life out in the countryside, 10 p.m. is usually deep-sleep territory. But Tokyo had other ideas — the city was just getting warmed up, buzzing with energy as if the night hadn't even started yet. Slightly overwhelmed, I transferred to the Keihin-Tohoku Line at Shinagawa and arrived at Oimachi. I checked into a nearby business hotel, spent exactly one minute in my room, and headed straight for the sauna. Tonight's destination: Shinagawa Sauna, the sauna inn where you can stay. It opened in June 2024 — back when I lived in Tokyo, it didn't exist yet. It had been on my radar for a while, talked about among sauna lovers across the country and even featured in sauna magazines. As I walked toward the facility, a sign reading "SAUNA" caught my eye. I ducked through the noren curtain, checked in, and made my way to the large communal bath. The footprint of the building is compact, so the changing area feels a little tight — but the sauna itself? No complaints whatsoever. The moment I stepped into the bathing area, the world shifted. There, at the center of the dimly lit space, sat three cold plunge baths: Little Mermaid at 19°C, Single at 8°C, and the neutrally warm Fukanyu at 30°C. Two sauna rooms — Ku (Sky) and Zen — wrap around the plunge pools. Climbing the stairs to the rooftop, I found a space that truly deserved to be called an oasis. A warm bath sat at the center, surrounded by more than 20 reclining and sitting chairs of various styles — you could pick whichever suited your mood. But what really made it special was the atmosphere. The ceiling and walls were blanketed in lush greenery, making it feel like you were taking an outdoor rest in the middle of a tropical forest. Many people were enjoying their post-sauna cool-down up there, and everyone looked completely lost in the experience. With a full tour of the place done, it was time to get in. Shinagawa Sauna has two sauna rooms: Zen, where you can do self-service löyly and the concept is all about turning inward, and Ku, where you can enjoy aufguss events and more. For my first set, I entered Zen. The room is themed around a Japanese tea ceremony, so the scent of tea drifts through the air, and the seating is tatami mat. There are even partitions to give each person a sense of private space. The concept of facing yourself is beautifully brought to life here. I sat on the tatami, closed my eyes, and focused on my breathing — and suddenly I forgot I was in the middle of one of the world's busiest cities. When I poured water over the stones for a self-service löyly, the scent of tea bloomed through the room along with a surge of steam. A facility that lets you do a tea löyly is genuinely rare anywhere in Japan, and I felt grateful for such a unique experience. After the sauna, I headed for a cold plunge — I chose Little Mermaid at 19°C. It sits at the center of the bathing area and you climb steps to get in, which reminded me of Yurakusu in Kumamoto Prefecture. This pool is 140 cm deep, specifically designed for full submersion. Most facilities prohibit going under, so the fact that this one actively encourages it was a genuine treat. I cooled myself thoroughly from head to toe, then headed up to the rooftop outdoor rest area. The atmosphere up there was, once again, remarkable. Gazing at the beautiful plants, I nearly drifted off to sleep — and sure enough, a few other guests already had, snoring softly. It's hard to blame them. The place really does feel like an oasis, and consciousness just... slips away. It made me realize that even in a compact urban space, you can create an experience of being at one with nature. You don't have to build a sauna in the middle of the wilderness — as Shinagawa Sauna shows, if you commit fully to a vision and bring it to life, you can offer something just as immersive. A good lesson. For my second set, I entered Ku, the aufguss sauna. The L-shaped bench faces two iki stoves. After warming up for a while, a staff member walked in carrying aromatic water. Then they addressed us all with something I'd never heard before: "We just finished an aufguss a little while ago, but it's Friday night and we're deep into the late hours — so I'd like to keep fanning until I hit my physical limit!" I'd never experienced anything like it. What hospitality. The other guests in the room burst out laughing. The staff poured the aromatic water over the stones, lemongrass filling the air with a beautiful fragrance — and then a wall of intense heat hit us. It felt like the staff member's pride and spirit were riding that heat wave, which somehow made it even hotter. When I'd had all I could take, I plunged into the cold bath. Resting on the rooftop afterward, I felt a deep sense of joy that this trip had started with such an extraordinary experience. An aufguss like that one — it's the kind of thing that only happens when you travel. Every facility has its own concept, its own character, its own design, and each experience carves itself deeply into your life. Especially in hot spring and sauna settings, where you are always the protagonist, where your mind and every one of your senses are engaged — those moments stay with you as vivid, lasting memories. That's exactly why sauna travel is impossible to quit. By the time I left Shinagawa Sauna and returned to the hotel after an exceptional sauna experience, it was past 1 a.m. When was the last time I was up this late? For someone living the quiet, retired life, it was a welcome jolt to the system. Occasionally disrupting your routine is important — or so I told myself as I stretched out on the bed, justifying the whole thing in my head. Before I knew it, I was fast asleep. Tomorrow, I'm heading to Saitama Prefecture first thing in the morning to visit an exceptional facility there.

Friday night: clocked out at 6 p.m., boarded a 8 p.m. flight, touched down at Haneda Airport at 9:30 p.m. A perfectly smooth sequence — sauna, cold plunge, outdoor rest — but make it a travel itinerary. I made my way from Haneda to Oimachi Station, and despite it being close to 10 p.m., the trains were absolutely packed. For someone like me who's been living a quiet, semi-retired life out in the countryside, 10 p.m. is usually deep-sleep territory. But Tokyo had other ideas — the city was just getting warmed up, buzzing with energy as if the night hadn't even started yet. Slightly overwhelmed, I transferred to the Keihin-Tohoku Line at Shinagawa and arrived at Oimachi. I checked into a nearby business hotel, spent exactly one minute in my room, and headed straight for the sauna. Tonight's destination: Shinagawa Sauna, the sauna inn where you can stay. It opened in June 2024 — back when I lived in Tokyo, it didn't exist yet. It had been on my radar for a while, talked about among sauna lovers across the country and even featured in sauna magazines. As I walked toward the facility, a sign reading "SAUNA" caught my eye. I ducked through the noren curtain, checked in, and made my way to the large communal bath. The footprint of the building is compact, so the changing area feels a little tight — but the sauna itself? No complaints whatsoever. The moment I stepped into the bathing area, the world shifted. There, at the center of the dimly lit space, sat three cold plunge baths: Little Mermaid at 19°C, Single at 8°C, and the neutrally warm Fukanyu at 30°C. Two sauna rooms — Ku (Sky) and Zen — wrap around the plunge pools. Climbing the stairs to the rooftop, I found a space that truly deserved to be called an oasis. A warm bath sat at the center, surrounded by more than 20 reclining and sitting chairs of various styles — you could pick whichever suited your mood. But what really made it special was the atmosphere. The ceiling and walls were blanketed in lush greenery, making it feel like you were taking an outdoor rest in the middle of a tropical forest. Many people were enjoying their post-sauna cool-down up there, and everyone looked completely lost in the experience. With a full tour of the place done, it was time to get in. Shinagawa Sauna has two sauna rooms: Zen, where you can do self-service löyly and the concept is all about turning inward, and Ku, where you can enjoy aufguss events and more. For my first set, I entered Zen. The room is themed around a Japanese tea ceremony, so the scent of tea drifts through the air, and the seating is tatami mat. There are even partitions to give each person a sense of private space. The concept of facing yourself is beautifully brought to life here. I sat on the tatami, closed my eyes, and focused on my breathing — and suddenly I forgot I was in the middle of one of the world's busiest cities. When I poured water over the stones for a self-service löyly, the scent of tea bloomed through the room along with a surge of steam. A facility that lets you do a tea löyly is genuinely rare anywhere in Japan, and I felt grateful for such a unique experience. After the sauna, I headed for a cold plunge — I chose Little Mermaid at 19°C. It sits at the center of the bathing area and you climb steps to get in, which reminded me of Yurakusu in Kumamoto Prefecture. This pool is 140 cm deep, specifically designed for full submersion. Most facilities prohibit going under, so the fact that this one actively encourages it was a genuine treat. I cooled myself thoroughly from head to toe, then headed up to the rooftop outdoor rest area. The atmosphere up there was, once again, remarkable. Gazing at the beautiful plants, I nearly drifted off to sleep — and sure enough, a few other guests already had, snoring softly. It's hard to blame them. The place really does feel like an oasis, and consciousness just... slips away. It made me realize that even in a compact urban space, you can create an experience of being at one with nature. You don't have to build a sauna in the middle of the wilderness — as Shinagawa Sauna shows, if you commit fully to a vision and bring it to life, you can offer something just as immersive. A good lesson. For my second set, I entered Ku, the aufguss sauna. The L-shaped bench faces two iki stoves. After warming up for a while, a staff member walked in carrying aromatic water. Then they addressed us all with something I'd never heard before: "We just finished an aufguss a little while ago, but it's Friday night and we're deep into the late hours — so I'd like to keep fanning until I hit my physical limit!" I'd never experienced anything like it. What hospitality. The other guests in the room burst out laughing. The staff poured the aromatic water over the stones, lemongrass filling the air with a beautiful fragrance — and then a wall of intense heat hit us. It felt like the staff member's pride and spirit were riding that heat wave, which somehow made it even hotter. When I'd had all I could take, I plunged into the cold bath. Resting on the rooftop afterward, I felt a deep sense of joy that this trip had started with such an extraordinary experience. An aufguss like that one — it's the kind of thing that only happens when you travel. Every facility has its own concept, its own character, its own design, and each experience carves itself deeply into your life. Especially in hot spring and sauna settings, where you are always the protagonist, where your mind and every one of your senses are engaged — those moments stay with you as vivid, lasting memories. That's exactly why sauna travel is impossible to quit. By the time I left Shinagawa Sauna and returned to the hotel after an exceptional sauna experience, it was past 1 a.m. When was the last time I was up this late? For someone living the quiet, retired life, it was a welcome jolt to the system. Occasionally disrupting your routine is important — or so I told myself as I stretched out on the bed, justifying the whole thing in my head. Before I knew it, I was fast asleep. Tomorrow, I'm heading to Saitama Prefecture first thing in the morning to visit an exceptional facility there.