Hottarakashi Onsen is a day-trip hot spring facility located at approximately 700 meters above sea level on a mountainside in Yamanashi City, Yamanashi Prefecture. Kocchi-no-yu (This Bath) opened in July 1999, and Acchi-no-yu (That Bath) was added in 2003. The name Hottarakashi means 'left alone,' reflecting the facility's minimal, handmade infrastructure operated by a small staff. The onsen is nationally famous for its spectacular panoramic views of the Kofu Plain, with Mount Fuji directly ahead and the illuminated Fuefuki River Fruit Park below. Kocchi-no-yu features an alkaline simple hot spring with pH 9.68, offering a tranquil atmosphere with Mount Fuji in full view. Acchi-no-yu has a strongly alkaline simple hot spring with pH 10.1 and is twice the size of Kocchi-no-yu, providing sweeping views across the Kofu Basin. The facility opens one hour before sunrise, allowing bathers to enjoy sunrise and morning glow from the outdoor baths, which is the greatest attraction. Approximately 400,000 visitors come annually. The four seasons offer distinct scenery: peach blossoms in spring, cool mountain breezes in summer, autumn foliage, and starry skies in winter. The alkaline water is gentle on the skin, retains warmth well, and is popular with visitors of all ages.