This is Dragon Falls, just north of Sakashita in Kawa Ue.
Yes, the weird foreigners jumped off it on a regular basis until the locals put up fencing around it to keep everyone in.
Let me tell you, that water is cold.
See the guy on the bottom left? That's where I jumped off from. It's about a 6 foot drop down, and that was more than enough for me. And, let me tell you, I thought I was pretty badass even doing that...
... at least until I slipped on the rocks, fell to my knees and almost bashed my head. Then, I felt distinctly less badass and much more scared for my life. I should have taken my clumsiness into account!
That was the first and only time I got into the waterfall, but I loved watching people jump into it. Such a magical, prehistoric looking place.