I recently watched this anime a few weeks ago and decided to give it a review as no one else has done so yet; so here goes!
Yuuna and the Haunted Hot Springs is your standard harem ecchi (and when I say ecchi I mean shiz tons of naked girls), with not to much of a serious plotline. Basically, a broke high schooler psychic called Kogarashi Fuyuzora gets a cheap room in a inn, but with one catch, he has to share it with a frequently naked ghost girl called Yuuna. Then starts the 'plot' in which Kogarashi gets beaten up regularly for being a pervert around all the hot, supernatural monster chicks that live there. The main girls are moe Yuuna, whos clutsy and cute; (your basic) tsundere assassin, Sagiri; a busty, alcoholic demon who's hella flirtatous called Nonko; your classic 'legal-ish' loli inkeeper, Chitose and some others whom I'm not too bothered to mention.
Anywho, this anime is a light hearted ecchi at its core, it doesn't need too heavy a plotline, as long as you like fan-service, you'll proberly enjoy this.