Lake Biwa turned out to be much closer than I thought - well, Ogoto-onsen wasn't that far up afield up the lake, but it's hardly 20 minutes away from Kyoto by local train on JR Kusei line. At the train station, we were picked up by the resort shuttle and headed straight to Ryokusuitei in less than 5 minutes away by car.
Biwako Ogoto-Onsen Ryokusuitei: http://ryokusuitei.com/
6-1-6, Ogoto, Otsu-shi, Shiga Prefecture, Japan
おごと温泉 びわこ緑水亭 滋賀県大津市雄琴6-1-6
(Feb-ulous Kyoto Part 9 - check out the whole series here!)