“Gensen kakenagashi onsen” refers to hot springs where fresh spring water continuously flows into the bath from a certified source. In this method, the water in the bath overflows and is not reused or recirculated. No circulation or filtration is conducted, preserving the natural properties of the spring. While the original temperature of the spring is generally used, minimal adjustments through slight heating or water addition are permitted to maintain a suitable bathing temperature. This allows bathers to enjoy the full natural benefits of the hot spring.