Located in the Hoshino Resort area of Karuizawa, this open-air onsen is nestled in a tranquil forest setting. Its baths are fed by a natural hot spring known since the Taishō era. The atmosphere is serene, with a modern design that blends seamlessly into the surrounding nature. Guests can enjoy both indoor and outdoor baths — especially relaxing after a walk through nearby Harunire Terrace.

Entrance fee: ¥1,350 (adults), ¥800 (children) — 2024 prices
💰 Estimated price range: ¥1,500–¥2,000
Touristy?: Popular but peaceful, especially on weekdays. A favorite among couples and families looking for a relaxing nature escape.