onsen between uno and kyoto/nara

Hi! I will be beginning my trip at the art islands, second destination will either be kyoto or nara – can you recommend an onsen that will be along the train route?

second question – I have 2 nights booked on naoshima (first night is at takamatsu airport), should I add another night there and travel in the morning, or should i leave at the end of my third day and start traveling towards kyoto? I have

booked hotels:
Nov 26 Takamatsu
Nov 27 Naoshima
Nov 28 Naoshima

Nov 30 (Ryokan Asukaso Nara – can move this date) this ryokan does not have a natural onsen

Dec 2 (Tokyo Bay)

by 92012770