Kazuma no Yu

An hour's bus ride from the nearest train station, this onsen on the border between Tokyo and Yamanashi Prefecture is likely to appeal most to hikers exploring the local trails. The facilities certainly don't merit a special trip, but Kazuma no Yu's alkaline hot spring waters should provide relief to aching limbs (not to mention a bewildering list of other ailments). If you're feeling peckish or have time to kill before the next bus arrives, you can grab a bite to eat at the onsite restaurant, where the menu makes extensive use of locally grown potatoes and maitake mushrooms.