Private onsen in Japan: what “in-room”, “open-air” and “free-flowing” really mean

• “A hot-spring bath in every room” does not mean an outdoor bath. Several hotels put an indoor tub by a large window that opens.
• “Open-air” is the word to look for if you want to bathe outside. Some ryokan have it in only one or two room types.
• “Free-flowing” (kakenagashi) is about circulation: the hotels below use it for a bath filled straight from the spring rather than recirculated. Whether the water is heated or diluted is a separate question — check both.
• “Private bath” in a hotel’s facilities list can mean a separate bath you reserve for a set time — at the three hotels shown below, for a fee — rather than a bath in your room.
• Shared baths may swap between men and women during the day, and some hotels do not let guests with tattoos use the shared baths.

These hotels all say every room has a hot-spring bath. What that bath is differs.

By contrast, at Hakone Suishoen all 23 rooms have an open-air bath, and at Hakone Gora Karaku all 70 rooms do. If bathing outdoors matters to you, look for the words “open-air” on the room page itself, not on the hotel’s front page.

The hotels below use kakenagashi for a bath filled straight from the spring, with the water not recirculated. Heating or adding water is a different matter: a hotel can state either, both or neither, so read the two points separately.

• Hakone Suishoen: the open-air bath in each room is filled straight from the inn’s own spring without recirculation. The shared open-air bath, by contrast, uses filtered, recirculated water.
• ATAMI Sekaie: every room’s open-air bath is fed directly from the Izusan hot spring, with no recirculation.
• Omuro no Mori Gyokusui (Ito): every room type has an open-air bath facing the sea, filled straight from the spring.
• Atami Izusan Karaku: for its shared view baths, the hotel lists no free-flowing bath, and states separately that the water is heated and has water added.

One hotel can do both. Suishoen’s rooms are free-flowing and its shared bath is not, so read which bath a statement refers to.

• Source: Hakone Suishoen, hot spring
• Source: ATAMI Sekaie, about
• Source: Omuro no Mori Gyokusui, rooms
• Source: Atami Izusan Karaku, hot spring

• Suiran Kyoto: 17 of the 39 rooms have a private open-air bath, with natural Arashiyama onsen water.
• Gora Kadan (Hakone): open-air baths come with certain suites and rooms, such as the Aoi, Fuji and Ume suites; the standard Japanese rooms are a separate group.
• HOTEL THE MITSUI KYOTO: of 160 rooms, only the Onsen Suites have a hot-spring bath; the other rooms have stone bathtubs.
• Atami Izusan Karaku: the ten Karaku Rooms have an open-air hot-spring bath. We have not checked the other room types, so this is not a statement that they lack one.

At these hotels the bath depends on the room type, so book the room type by name and read its own page.

• Source: Suiran Kyoto, guest rooms
• Source: Gora Kadan, rooms
• Source: HOTEL THE MITSUI KYOTO, rooms and suites
• Source: Atami Izusan Karaku, Karaku Room

Some hotels also have baths that one group at a time can book. They are not in your room. At the three hotels below, they cost extra.

• Hakone Gora Karaku: three private baths (Hinoki, Iwa and Silk) can be reserved for a fee. The Silk bath is not hot-spring water.
• Suiran Kyoto: two private open-air baths, Raku and An, can be reserved for 45 minutes at a time for a fee.
• HOTEL THE MITSUI KYOTO: a private onsen for staying guests, with a mist sauna, can be booked for a fee, 7:00–23:00.

• Source: Hakone Gora Karaku, hot spring
• Source: Suiran Kyoto, guest rooms
• Source: HOTEL THE MITSUI KYOTO, thermal spring and spa

• At FUFU Atami the two shared open-air baths swap between men and women each day; at Hakone Gora Karaku the two shared baths also swap. If you want to try both, check the times.
• HOTEL THE MITSUI KYOTO’s Thermal Spring spa is used in a swimsuit. It is not a bath you enter naked.
• FUFU Atami does not admit guests with tattoos, or children in nappies, to its shared open-air baths. Every room there has its own open-air bath.

• Source: FUFU Atami, hot spring
• Source: Hakone Gora Karaku, hot spring
• Source: HOTEL THE MITSUI KYOTO, thermal spring and spa

• Open the page for the exact room type you will book, and look for “open-air” or “semi-open-air” there.
• Check whether the room’s water is hot-spring water at all, and whether the hotel calls it free-flowing.
• If a “private bath” is listed under facilities, check whether it is in the room or a bath you reserve, and whether it costs extra.
• If you have a tattoo, read the hotel’s rules for each place you plan to use, including the bath in your room, and ask before booking if they are unclear. See where hotels’ tattoo rules apply.

For a list of properties where we have found an in-room hot-spring bath, see ryokan and hotels with a private onsen. For Hakone, the Hakone page groups inns by how private the bath is.