The moment I woke up that morning, I heard a voice deep within my body calling out for "heat." A punishing, intense heat, followed by a cold plunge bath sharp enough to shock me awake. A half-hearted lukewarm bath had no place in my plans for the day.
The night before, I had holed up in the meditation sauna at Tsurumi Ryokuchi Yumoto Suishun, calmly aligning body and mind in the silence. But once morning came, a different desire reared its head. I was craving the exact opposite of meditative calm: rough, savage heat. A facility that perfectly matched that kind of morning came to mind: Utopia Shiratama Onsen. Open from 6 a.m., with a reputation for both fierce sauna heat and a wonderfully refreshing cold plunge, it checked every box. Without hesitation, I chose this spot for my morning sauna session.
Utopia Shiratama Onsen is a sento that has been beloved by the local community in the Kyobashi area of Osaka since 1963. Under the second-generation owner, the building underwent a major renovation, and under the third generation, it evolved to feature a Bona sauna. Despite being deeply rooted in the local community, its one-of-a-kind ice bath has drawn passionate attention from sauna enthusiasts across the country.
After getting ready and checking out, I drove toward my destination.
When I arrived, I found an exterior that perfectly embodied the classic sento sauna. Stepping inside, the nostalgic atmosphere of an old-fashioned bathhouse remained, but it had clearly been renovated and kept impeccably clean. Looking at the walls, I noticed autographs from numerous celebrities, including professional baseball players. This was clearly a rare sento loved not only by local regulars but by famous figures as well. What kind of totonou state awaited me here? I passed through the noren curtain, changed, and entered the main bathing area.
Being a sento, the scale is by no means large. But everything necessary is packed tightly within it. A variety of tubs, including an electric bath, a Bona sauna boasting intense heat, a deep cold plunge into which ice is poured, and rooftop outdoor relaxation space. There is no compromise whatsoever in the setup designed to achieve totonou. Even though it was still early morning, the place was bustling with customers. About half of them already appeared to have lost consciousness in the outdoor relaxation area. I, too, would soon be joining their ranks.
I stepped into the sauna for my first round. The instant I entered, I was nearly overwhelmed by the intense heat. It might have been a bit too much stimulation for a body that had just woken up. That's how fierce the heat was. The sauna at Utopia Shiratama Onsen uses the Bona sauna method, a distinctive design with heaters housed beneath the benches. The thermometer hovered around 90°C, and an automatic löyly was set to fire at a rapid pace of once every 10 minutes. Just sitting there, the humidity kept climbing, making the perceived temperature feel even higher than the number on display.
After about five minutes, I had worked up quite a sweat. On top of that, the lighting in the sauna room shifted, signaling that a heat wave was about to be sent in. That was my limit. I immediately stepped out and headed straight for the cold plunge.
The cold plunge sits at zero distance from the sauna room. The cold plunge at Utopia Shiratama Onsen is itself a famous attraction, drawing sauna fans from all over the country who come specifically for it. Said to be Japan's first "ice bath," it's quite deep, at 140 centimeters. Ice is added periodically to maintain an ice-cold state. When I used it, no ice happened to be added, but the water temperature was still a satisfyingly cold 14–15°C. I was instantly enveloped in a wave of refreshment, after which I made my way up to the rooftop outdoor relaxation space.
Relaxing outdoors first thing in the morning while gazing at the Osaka sky is a supreme experience. Ferociously hot sauna, crisply cold plunge. That contrast multiplies the pleasure of the outdoor rest many times over. I felt something close to the bodily sensation I once experienced at Ogaki Sauna in Gifu Prefecture. Craving this kind of intense contrast on a regular basis is simply the nature of a sauna enthusiast, I suppose.
Before my second round, I looked around the bathing area and saw a man who looked like a salaryman fresh out of his suit, an elderly man who was clearly a regular, and men covered in tattoos head to toe, all sweating just like me and enjoying the same refreshing cold plunge. Despite their obviously different ages, positions, and occupations, none of that mattered in the slightest within this bathhouse.
I've come to believe that the main bathing area of a sento is the most equal place in the world. Within its walls, age, status, title, and hierarchy all become meaningless, and everyone equally enjoys the cycle of sauna, cold plunge, and outdoor relaxation, everyone equally reaching that refreshed state. I sometimes exchange words with people I've just met, but because we share this naked camaraderie, there's no way to know who they really are outside these walls. No excessive formality, no titles required. What emerges there is pure communication between fellow lovers of onsen and sauna. This is the very essence of Japanese sento culture, and I find myself once again struck by what a wonderful culture it truly is.
For my second and third rounds, I repeated the same cycle, alternating between the scorching Bona sauna and the ice bath.
If I lived near here, I would repeat this cycle endlessly every day: heating my body to its limit in the intensely hot Bona sauna, cooling it down in the famous cold plunge, and finishing with outdoor relaxation on the rooftop. That's how simple yet perfectly refined this sento truly is.
Even after finishing my morning sauna session, I still had plenty of energy left. So I decided to hit up one more facility right away.
My next destination was SPAWORLD HOTEL&RESORT. From a small, community-rooted sento to a massive facility boasting one of the largest scales in the country. This very gap is what makes sauna trips so fascinating. From last night's quiet meditation sauna, to this morning's scorching Bona sauna, to the massive spa famous for its sheer size that I was about to visit. Even though they're all called "sauna," the experiences are completely different from one another. It's precisely because you can savor this full range of contrasts that a sauna trip in Osaka never gets old.
