Boun is a long-established hot spring inn that was founded in 1599, the year before the Battle of Sekigahara. It must have been a key player in the prosperity of Kusatsu during the Edo period. Jippensha Ikku wrote about the inn's prosperity in "Joushu Kusatsu Onsen Dochu," and the haiku poet Issa, who was an old acquaintance of the seventh owner, wrote about the splendor of the hot springs as "the face of the moon unclouded by the steam." The inn offers six free-flowing baths that draw water from two hot springs.

The atmosphere of the bathhouse is wonderful. At Nishi-no-yu, which is fed by the Sainokawara hot spring, you will be captivated by the gazebo-style open-air bath and the beautiful wooden-framed indoor bath. Bandai-no-yu, which overlooks the inn's prized garden, is also very tasteful. I wonder what it would be like in May when the rhododendrons are in bloom. The highly acidic Kusatsu Onsen hot spring flows into the indoor and open-air baths, and is typical of Kusatsu Onsen, with its strong antibacterial properties. The elegant Yusan-no-yu allows you to see the difference between the two hot springs. The Sainokawara hot spring and the Bandaiko hot spring flow into the baths next to each other. Men and women alternate between baths. You can indulge in the hot springs to your heart's content.

The splendid wooden-framed interior has a modern look decorated with flower arrangements and wildflowers. The most popular room is the "Unshoan" room with an open-air bath. It is equipped with a Japanese-style room, an adjoining room, a shower room, and a wooden terrace overlooking the garden, and the open-air bath that leads to the garden is filled with water from the Sainokawara hot spring.