Ozu Castle is the only castle keep in Japan you can book a night in. It stands above Ozu, a small town in Ehime on Shikoku, where the Hiji River loops through a valley people here call Garyu, the reclining dragon. The keep was dismantled in the Meiji period and rebuilt in 2004. Not in concrete, which is what most Japanese castles got, but in wood, worked out from surviving sketch maps, a carpenter's scale model and photographs taken in 1877. The joinery uses no metal nails. UNESCO listed that carpentry as Intangible Cultural Heritage in 2020. Forty percent of the money came from Ozu residents. Overnight, the keep, the two original turrets, both Important Cultural Properties, the hill and the bath are closed to everyone but you, your butler and your chef. The arrival is staged. You are met at the gate, dressed in armour and walked in, and gagaku is performed under the floodlit tower. Dinner is reconstructed from the Kato family's records and served on local Tobeyaki ware. There is a nightcap in the moon-viewing turret. Then you sleep in the keep, on cypress. Breakfast is at Garyu Sanso, a villa down by the river listed in the Michelin Green Guide. The Edo and Meiji merchant streets in town are worth an hour afterwards.

Fukuyama Castle Park sits beside Fukuyama Station in Hiroshima Prefecture, which is part of what makes the arrangement odd. For one night the whole park closes and there is nobody in it but you. Several of the buildings inside are nationally designated Important Cultural Properties. The role you are given is lord of the castle, and the evening is built around that rather than around sightseeing. You bathe in the Oyudono, the lord's bathhouse, which went unused for centuries before it was brought back. It is an Edo design, closer to a steam room than a hot bath, so it takes a few minutes to settle into. Dinner began as a thought experiment. When Perry's delegation landed at Uraga in 1853, the man who received them was Masahiro Abe, lord of Fukuyama. Had they come to Fukuyama instead, what would he have put in front of them? The chef worked from period recipes and local ingredients to answer that. There is more in the area than most visitors realise. Noh and other performing arts are still active here, Tomonoura is a short drive along the coast, Kinoshita-Tenjin Shrine is quiet even in season, and several streets of merchant houses survive intact. A concierge builds the rest of the stay around what you want to see.

Marugame Castle stands on a wooded hill called Kameyama, above the town of Marugame in Kagawa, on Shikoku. It has been there for over four hundred years. Two things make it unusual. The wooden keep is original, one of only twelve left in Japan and the oldest on Shikoku. And the stone walls holding it up are the tallest of any castle in the country. The Kyogoku family held Marugame for two centuries. For one night the castle, the gate and the ramparts are closed to everyone but you. You come in through the Taikomon, the drum gate built in 1670. A drum has marked the hours there since the Edo period, and when it sounds for your arrival the Marugame Taiko group starts up. Dinner is at Enjyukaku Bekkan, looking down over the old castle town, built from dishes in the Kyogoku household records and whatever the Seto Inland Sea has that week. Afterwards the keep itself opens as a private bar. You sleep at Enjyukaku Bekkan as well. It is a single-storey wooden house put up in 1933 using material from the Kyogoku family's Tokyo residence, and the ceilings, transoms and metalwork all came with it. Breakfast is at a teahouse inside Nakazu Bansho-en, a daimyo garden ten minutes away.

GORA KADAN stands on land that belonged to the Kan'in-no-miya, one of Japan's imperial families. The villa they built here in the early Showa years is still standing, and it is where dinner is served. The ryokan is a Relais & Châteaux house and carries its inheritance without making a fuss about it. Pale wood corridors, traditional materials cut on modern lines, and a garden that was a private imperial garden a century ago. Three springs feed the baths, two of them rising inside the garden itself, and the water is gently alkaline. Many rooms have their own open-air bath. There is a large public bath that changes over at night, and a private open-air bath you can reserve, filled straight from the source, with a steam sauna beside it. There is also an indoor pool built like an orangerie, a warm-stone sauna and a spa. Dinner is kaiseki in the old villa, and the menu turns over with the month. Sushi Kadan, the counter, is there if you would rather eat that way. Gora is high on the Hakone slope, inside the national park, under two hours from Tokyo by car. The switchback railway, the cable car and the art museums are a short way down the hill.

Atami has been a hot-spring town for about fifteen hundred years, on the Sagami Bay coast, and it has stayed in fashion through the shogun era and the whole of the twentieth century. It is still the quickest real escape from Tokyo: about ninety minutes by road. THE HIRAMATSU sits on a headland above the bay. The building went up in the 1980s as a private state guest house, in sukiya style, by the master carpenter Koichi Kinoshita, and only became a hotel later. That history shows in what is absent. No gloss, no ornament. Plain wood, tea-room proportions, and terraces where the water sits still enough to hold the sky. Thirteen rooms, every one facing the sea. Each has its own bath fed by Atami's spring water: a granite tub half open to the air beside a wide window in most rooms, and in the two suites a bath set in a garden with nothing overhead. Dinner is French, which is the surprise. It is served in a sukiya dining room above the water, built on kinmedai landed at Atami, Amagi black pork and black truffle, from a cellar the house is quietly proud of. A Japanese building with a French kitchen in it sounds like it should not work. It does.

In Hakone, the mountains are the main event — and Gora is where you climb up into them to rest. KARAKU stands in Gora, the okuzashiki — the quiet inner sanctuary — of Hakone, high in the Fuji-Hakone-Izu National Park yet less than 100 km from Tokyo — under two hours by road. From here the Hakone range rolls away toward Sagami Bay, the seasons turn in full colour, and the volcanic valleys and lakes that made this one of Japan's great hot-spring retreats lie just beyond the ridgelines. Gora itself is a hillside of sights — the switchback mountain railway and cable car, gardens and art museums — all within easy reach for the days around your stay. This is a house built around the bath. Your room comes with its own private open-air hot spring — and each way to soak here has its own character. The observation baths, among the largest in Gora, open wide onto the mountains; the private baths, reserved just for you, wrap you in quiet; and your own room's spring is there at any hour, with no one to wait for. Bathe where the mood takes you. Between soaks there are terraces laced with water and light, a bamboo forest walk, and a guest lounge where drinks and light bites are simply there for the taking. When evening comes, the mountain sets the table: seasonal kaiseki at the main dining room, from a kitchen led by a chef whose career runs through celebrated houses — the Imperial Hotel among them — and the service of distinguished guests; or premium meat and seafood grilled before you on the annex's top floor, looking out to Mount Myojogatake. This is a one-night stay built around doing beautifully little — arrive, bathe, dine, and let the mountain quiet do the rest.

Some stays are measured not by how much you see, but by how completely you stop. LIEN sits on the Futomi shore of Kamogawa, in Chiba — barely two hours from central Tokyo, yet a world away, with the Pacific opening out in front and the green Minegoka hills rising behind. It is a small house of just ten detached villas, and every one has its own private open-air hot spring. No communal bathhouse, no waiting, no other guests in sight — only you, the rising steam, and the changing blue beyond the rail. The name LIEN comes from the French word for "bond." It reflects how this house sees hospitality: not the greeting of a passing traveller, but the keeping of a genuine connection — with its guests, and with the sea and mountains that feed its table. LIEN began as a fish shop, and that trade still shows on the plate: the finest of the Boso catch, served course by course in the quiet of your own private dining. A night here is short on programme. You arrive, you bathe, you eat, you sleep with the sea audible through the window, you bathe again in the morning, and breakfast is not at a fixed time. That is all of it. It suits people who have been moving for a week and need to stop, which usually means after Tokyo rather than before it.

Most of Kyoto's visitors never make it this far north. ROKU stands in Takagamine, in the wooded hills of Rakuhoku, held between three mountain peaks and threaded by the clear Tenjin River. Its name carries the place twice over: roku, the foot of the mountains, and roku, to strain paper — for this river was once the Kamiyagawa, where papermakers worked its waters a thousand years ago. It is the Asian flagship of LXR — Hilton's collection of one-of-a-kind luxury houses — and a Forbes Travel Guide five-star hotel. Yet what people remember is something quieter, and rarer: an outdoor thermal pool fed by natural hot spring, open in every season, where you swim in swimwear beneath the open sky — together, not parted for separate baths — and watch the steam lift into the cold on a winter's morning. A hot spring you can swim in is a rare thing in Japan; here, it is the heart of the place. Low, contemporary architecture steps down toward the river, and the forest comes right to the window. And here is the secret most visitors miss: the Golden Pavilion of Kinkaku-ji is only about fifteen minutes away on foot — close enough to walk over as the gates open, ahead of the crowds, or the moment the first snow falls. With two nights here, the quiet north of Kyoto opens up around you.