This onsen is on the beach! The combination is perfect, you can soak in the onsen while listening to the waves crash onto the beach. Some of the most relaxing moments I have ever experienced. The onsen baths are built into the rocks so you feel so close to nature. If you go in the summer, you can also head down to the beach. Unlike most beaches you will find in Japan, there isn't that much trash and the sand is a nice color. There are a lot of activities you can do in Shirahama as well. Getting here is easy too since there's an airport.