At this coastal Japanese hotel, one unexpected detail stole the entire show

More than 50 years after the hotel first opened on the Sandanbeki Cliffs above the town of Shirahama in Japan's Kii Peninsula, the property was reborn in 2017 as the luxurious Infinito Hotel & Spa. About 630 kilometres south-west of Tokyo, the hotel is a popular rejuvenation stop for affluent hikers who have completed the Kumano Kodo pilgrimage trail.

Both my bedroom and the hotel's Pacific Lounge lobby bar boast floor-to-ceiling windows overlooking Kanayama Bay, the Pacific Ocean, the Kii Mountain Range, and the "bubble-era" extravagance that is the fairy-tale Baroque-style Kawakyu Hotel. I could sit staring at the view all day, if it weren't for the treat awaiting me on my balcony.

The decor in Infinito's public spaces plays to the Japanese nostalgia for the innocence, affluence and artistry of the Taisho era (1912-1926), before World War II devastated Japanese society and culture. Adjoining the lobby, the Peak Bar (a smoking lounge!) and the Library have an oddly familiar ambience, somewhere between a colonial gentleman's club and a yacht club.

The Library includes a leather-bound set of Encyclopedia Britannica and also, mystifyingly, a paperback guide to the birds of Costa Rica.

I was delighted to discover that my balcony had its own private onsen ("for couples, families, tattoo wearers"). That's right: I had the barely conceivable luxury of a personal open-air spa, fed by the reputedly healing waters of Shirahama's nationally famous 1400-year-old hot springs, directly outside my bedroom. At first chance, I jump into the bath - then immediately jump out, because I had not quite realised how hot hot springs really are. I run cold water into the onsen then immerse myself again, more slowly this time. It is marvellous, so I rinse and repeat, then rinse off again in the shower, and flop onto my supremely comfortable bed, feeling younger, softer, and just better all over.

Otherwise the room is spacious and clean, minimalistically decorated and quiet, and I could lock myself in there for a week. My only disappointment was that a machine I mistook for a domestic robot was actually a portable air-conditioner, with which I found it impossible to form a meaningful relationship.

The hotel is about seven kilometres outside the pleasant resort town of Shirahama, but really it's a "wellness" (I hate that word) destination in itself. Even if you don't have your own private onsen, the hotel offers men's, women's and mixed infinity baths, and a garden pool.

My own personal onsen.

The writer travelled as a guest of the Kii Peninsula Tourism Authority