Jōmon natural onsen - Shiraku no yu

A wooden, creaky, worn, and dimly lit onsen complex. But that's not a minus — it's just its character, for those who aren't into neon lighting and smooth plastic surfaces. There are two baths: one indoors and one outdoors. Plus a barrel bath. I didn't check the temperature, but it was just right for me (meaning hot water fans might find it too mild). There's a sauna. And a small rest area with onigiri and tatami. If you want a proper dinner, there's a restaurant attached next door (I didn't go myself). There's parking, but I'm not confident it'll have free spots during peak hours. The lack of English pretty much anywhere was a concern, and the Japanese signs are written in a pretty distinctive font, so if your Japanese isn't great, there might be some discomfort. But overall it's a good place.