Hirauchi Seaside Onsen (平内海中温泉) literally means an "Onsen in the Sea" in Japanese. It is maintained by the local community and a donation of ¥100 is requested.
One really has to choose the timing to go, as the onsen will be filled with seawater during high tides. Apparently, the water temperature can get very hot at low tides.
According to the young and friendly boss of Sanpotei restaurant (散歩亭) located in Anbo port (安房港), as the area is completely dark at night, star-gazing while soaking in the onsen will be an unforgettable lifetime experience.
Onsen during sunrise.
On my first attempt to visit the onsen, the pools had already been drained when I arrived, and the locals were seen busy scrubbing the onsen rock pools. One of the them told me that the pools would not be ready that soon. So, I had to abort mission and took a nice stroll in the area instead.
As I was living in a campervan during this trip, I decided to try again and wash up at the onsen the following morning. It was a cool cloudy morning, and I was greeted by a lovely sunrise when I arrived at the onsen. To my further delight, there was no one around, which meant I could have the whole place to myself!
Without further hesistation, I got myself ready and took a dip in the onsen; but to my disappointment, the water was lukewarm. Bad timing. The tides were already coming in. It was then that I figured out why I was the only person there at that time.
In the end, I just had a brief soak in the main pool, and did a quick wash-up at the smaller but hotter mini-onsen at the side.
Considering that I managed to tick off an item from my bucket list, and had a wonderful sunrise, it was still a worthwhile experience, I guess.
Entrance to the onsen with basins, a donation box, an information board and reminders to not wear anything in the onsen.
Locals cleaning and maintaining the onsen during low tides.
Enjoying the sunrise!
Type: simple sulphurous spring
Source: natural flowing spring
Flow rate: -
Minerals: -
Osmotic pressure: -
pH: -
Source temperature: -
Indications: neuralgia, skin disease, rheumatism, etc.
Experience (体験) : 4/5
Ambience (雰囲気) : 5/5
Rustic charm (野趣) : 5/5
Accessibility (アクセス) : 4/5
Price (値段) : 5/5 [Free/¥100 donation]
Around 30min via national highway 77 from Anbo port by car.