Originally Posted by
RichardInSF
How about the Hakone area? For a less touristy experience, maybe on the Izu or Boso peninsula, although I don't know even if there are onsen in those places. I am sure a few experts on these areas will soon weigh in.
There are vast amounts of ryokan in the Izu area, it's very popular with Japanese but less so with foreigners (who are drawn like moths to Hakone instead). Search for ryokan in eg. Atami, Mishima, Shimoda, Shuzenji.
Can't say I've ever heard of any onsen or ryokan in the Boso area? But if you head further up north, Nikko and nearby (Kinugawa, Chuzenji etc) is definitely an option though.