Koraku Onyado Fujiginkei Hotel

The rooftop open-air bath, Fujimi-no-yu (富士見の湯), sits on the top floor with a clear line across Lake Kawaguchi to Mount Fuji, the lakeside lights showing at night and the mountain catching the first sun at dawn. Downstairs, the indoor bath, Meiseki-buro (銘石風呂), is walled in rough natural rock, and a slow soak against the stone warms you to the core. Both baths draw on a spring the ryokan calls Reisui-no-yu (霊水の湯). It's a stay-focused ryokan on Lake Kawaguchi's north shore, and the same Fuji view carries from the guest rooms through to the baths. Most people come for a half-board night: dinner, a room facing the mountain, and a soak before bed or before breakfast.