We love, love, love this park! I'm not sure of the name. I was in Takeo following the road signs for Utagaki Park, but those sign ended and I followed a sign that read Dog Mountain (犬山) in kanji. At the top of the mountain was this park.
The rollerslide at this park is one of the fastest we have been on and it has the added benefit that it swerves in and out of a wooded area. It was really neat! There is also an obstacle course that you can now run through. The first time it was too over-run with weeds.
I forgot to mention the view!!!