In 1866, a former samurai stuck bamboo pipes into the lake bottom and was able to extract the hot spring water into a barrel on a boat above. It was an open-air spring bath on the rocking boat.

This continued for some years until they finally reclaimed some land offshore in 1886 and drew the hot spring water directly below and even built a ryokan inn above. This was the start of commercial operations as "Asozu Onsen" (浅津温泉).