Kirishima Yunotani Sanso

I've visited more than 200 onsens in Kyushu, and this is the best one for me. The water is incredible, with hot, medium, and cool baths, plus sulfur water and carbonated water. It gets pretty busy in the morning, with lots of locals. Maybe try going around 11 or 12 in the afternoon, when it could be quieter.

The water here is among the best hot spring water in Japan, maybe the best I've ever had. There's a tepid carbonated bath and a hot sulfur bath.

Once you get the hang of moving between the three baths, it gets addictive. They're set at hot, lukewarm, and cold, and little wooden pieces like railroad ties can be placed between them to adjust the temperature. On my first visit, there weren't any pieces nearby, so I wasn't sure how to bathe. The hot one was too hot, while the lukewarm one felt too cold at around 37°C, and I thought it might be tough for a beginner. When I came back the second time, someone had put a piece of wood there, and I figured out how to get the temperature just right. I stayed overnight and didn't run into anyone else, so I had the place all to myself.

The inn has a washing machine and kitchen. The large public bath is open at night, and there are 100 yen lockers outside it. The water is a mix of a sulfur-carbonated cold spring, the sulfur spring at around 41-42°C, and a lukewarm bath between them. There are two washing spots at the back. Nothing is heated or diluted. The spring is weakly acidic and simple sulfur water, with a source temperature of 44.1°C and pH 5.6. A 30-minute open-air bath is available by reservation. The source is a short distance away, and its water comes out at just the right temperature, flowing from a spout into the tub. It's lovely to watch the amount of sulfur-carbonated water rise and fall, almost like the spring is breathing. A great hot spring. One of the inn's cats comes by to work in the evenings, and it's very friendly and adorable.