Threadbare but exceedingly homely, this family-run guesthouse offers good-value tatami rooms, indoor and outdoor onsen with divine volcanic waters, and a wealth of information on local sights and hiking. Take the T-course bus to Senkyōrō-mae from the east exit of Odawara Station (lane 4; ¥1050, 50 minutes); it's a one-minute walk from there.
A smart choice, geographically-speaking, if you're planning onward travel by bus to the Fuji lakes region.