Kusatsu Hot Spring Best water volume in Japan (natural discharge) The total volume of more than 100 discharge points reaches over 32,000L/min. Over-flowing natural hot spring water is 100% natural spring water: No heating, diluting or circulation system has been installed and the onsen water is cooled naturally. Very strong sterilizing power. The acidity is so high that a 1 yen coin (made of aluminum) can be dissolved... Discovered by Koshiro Tanaka at Oazakusatsu, Agatsuma District, Japan