Oko Yusui is one of the 100 best water in Japan. Because it is so soft water, even small life cannot live. Therefore, it is very pure water.
Oko Spring (大川湧水) is one of the 100 best water located in Yakushima Island. It is very soft water because it doesn't contain much minerals. It is located near Oko Falls.
Tourist Info.
There is parking. No restroom.
You can drink this water.
Access
0. at any Bus Station.
1. use local bus to Okonotaki.
2. walk
15 min
New Wave Samurai Movie. 
映画好き集まれ！ 
Oko Yusui is one of the 100 best water in Japan. Because it is so soft water, even small life cannot live. Therefore, it is very pure water.