Tosa and Susaki Day-Use Onsen: Sanyoso or Sodayama?

These two baths are often grouped as day trips west of Kochi City, but they suit different days. Sanyoso is the better fit for the coast, the 36th temple on the Shikoku Pilgrimage and a soak beside Tosa Bay. Sodayama makes more sense if you are heading through Susaki and want a forest setting, a low-temperature cypress bath and a simpler station transfer.

Both are inn baths open to day visitors, not large spa complexes. Think of this as a choice between location and water character; neither is an efficient add-on to a short city stay without a car or a carefully checked public-transport plan.

At a glance

Choose Sanyoso for the coast and the warmer, salt-rich spring

Sanyoso stands in Usa, Tosa City, close to the 36th temple, Seiryuji. Its spring is classified as a sodium-calcium chloride hot spring. The operator says the water turns a yellow-brown colour when exposed to air and gives an average source-outlet temperature of 42.5°C. If you are looking for a distinctly mineral-rich, warmer bath after a coastal drive, that is the main reason to choose it.

Face towels are sold for ¥110 and bath towels can be rented for ¥110. Shampoo, conditioner and body wash are provided.

Sanyoso’s baths alternate between men and women every other day, so the outdoor bath and the single-person pot baths are not necessarily on the side you will use that day. The operator specifically identifies the outdoor pot bath as source-fed. It describes the spring more broadly as free-flowing, while local tourism listings describe the public bath water as circulated and filtered. The published information does not resolve how each tub is treated, so don’t assume every bath is untreated source water.

There is also a free footbath by the entrance, with the beach at Ryū-no-Hama just across the road. You can enjoy that stop without entering the shared bath. Sanyoso does not admit bathers with tattoos, according to its current bath information.

Pick Sodayama when the mountain bath is the point

Sodayama sits in Kuwatayama, Susaki. Its water is classified as an alkaline simple sulfur cold mineral spring, with pH 9.5. The cold-spring label refers to the source classification, not to every pool being cold: the public baths include indoor and outdoor pools, as well as a low-temperature cypress bath supplied directly from the source. The operator lists that cypress bath for day visitors on both sides.

Check the day-use schedule for holiday changes.

This is a small inn in a wooded valley, not a multi-pool spa. The public day-use bath has no sauna or reservable private bath. Some guest rooms do have private spring baths, but those are part of an overnight stay and should not be confused with day-use access.

Getting there: Sodayama is easier by rail, but book the pickup

Sodayama lists JR Agawa Station as its nearest station, about six minutes away by car. A station transfer is available, but it must be arranged in advance by phone. Confirm that the pickup can be arranged for your day-use visit and coordinate it with the train; the published page does not give a fixed shuttle timetable. The inn has free parking for 30 cars.

Sanyoso’s complimentary shuttles from Kochi Station and Nakajima bus stop are restricted to guests booked on a one-night, two-meal plan, with advance reservation required. Day visitors should not build their plan around that service. Tosa City’s Dragon Bus serves the Usa and Ryū area, but departures are limited and vary by route and day. Check the city’s current timetable and confirm the walk from the stop before relying on the bus for a bath visit.

If travelling without a car, Sodayama is the more plausible choice because it can arrange a pickup from Agawa Station. It still requires advance coordination. For a straightforward public-transport outing, compare the day-use baths in Kochi City instead.

Let the rest of the day decide

Pair Sanyoso with Seiryuji, Usa’s coast or a drive along the Yokonami Kuroshio Line. It is a poor detour if your day is confined to central Kochi and you have no car. Sodayama fits more naturally around Susaki, including a stop for nabeyaki ramen, or a westbound drive toward Shimanto.

The ticket difference is small: ¥50 between Sodayama and Sanyoso on a Sanyoso weekday, or ¥150 on a weekend or public holiday. Choose for the spring and route, not the admission fee. If you are continuing farther west, the Hata-region day-use onsen guide covers baths around Shimanto, Tosashimizu and Sukumo.

Sources

- [Sanyoso: current day-use prices, hours, spring classification, amenities and tattoo policy](https://sanyo-so.co.jp/spa/) - [Sanyoso: official spring description, colour change and 42.5°C source-outlet average](https://sanyo-so.co.jp/leisure/105/) - [Sanyoso: access and overnight-guest shuttle restrictions](https://sanyo-so.co.jp/access/) - [Kochi Prefecture Tourism: Sanyoso day-use prices and hours](https://kochi-tabi.jp/search_spot.html?ID=7932) - [Niyodo Blue Tourism: Sanyoso facilities, day-use details and access](https://niyodoblue.jp/experience/detail.php?id=40) - [Sodayama Onsen: day-use prices, hours and bath facilities](https://sondayama.co.jp/dayuse/) - [Sodayama Onsen: spring classification and pH](https://sondayama.co.jp/onsen/) - [Sodayama Onsen: access, Agawa Station pickup and parking](https://sondayama.co.jp/access/) - [Tosa City: current Dragon Bus routes and timetable links](https://www.city.tosa.lg.jp/life/detail.php?hdnKey=6165) - [Kochi Prefecture Tourism: Sodayama day-use prices and Thursday hours](https://kochi-tabi.jp/search_ryoma_pass.html?id=8176) - [Kochi City day-use onsen and sento guide](/guides/kochi-city-onsen-sento-guide/) - [Hata-region day-use onsen guide](/guides/hata-shimanto-tosashimizu-day-onsen-guide/)

Checked: 2026-09-28

Tags: Tosa onsen, Susaki onsen, Kochi day-use onsen, Sanyoso, Sodayama Onsen, Yawaragi, Shikoku hot springs, Tosa Ryū Onsen, day trip from Kochi, day-use bath, sulfur spring, chloride spring, onsen access, Japanese onsen, Kochi travel