Marukoma Hot Spring is a secluded retreat located on the shores of Lake Shikotsu in Hokkaido, known for its tranquil atmosphere and natural hot springs. Established over 100 years ago, this spot offers an authentic onsen experience, with outdoor baths that open directly onto the lake, providing stunning views of the lake surrounded by mountains.

Actually, this is a hotel, but you don’t have to stay there to enjoy the onsen. Just be sure to check the open hours for non-hotel guests on their website.