Seseki Onsen is located approximately 22 km north from the Rausu town center along Prefectural Road 87, about 2 km before the road's end at Aidomari.

Although called an onsen, it is not an inn but simply a pool constructed with stones in the sea. It is a wild and dynamic hot spring where bathing can be impossible due to the tides (it is submerged in the sea at high tide) or the water can be too hot (as the 64°C source water is not diluted at low tide).

It became known nationwide after appearing in the TV drama 'Kita no Kuni Kara' (From the Northern Country), and it is visited by hot spring and hidden spring enthusiasts from all over Japan.

Bathing in Seseki Onsen requires some know-how, so it is recommended to gather information from related websites before attempting to enter.

*The onsen is located on a site managed by kelp fishermen, so please ask for permission before bathing. Please bathe with good manners.