I believe this is the park someone commented on a few posts ago.... Thank you!!! It's called Sarayama Park and it's in Saza right off 204. If you drive back just a little bit, you'll find a big parking lot. Once you park, you can either follow the hordes of children pulling their parents by the hand, or follow the signs to Family Land.
This rollerslide is more bark than bite... at first. Several of the spots have rollers that just don't move. It's very slow going... until you hit the section in the picture above!
As you can see, the park is quite expansive. My vantage point for this photo is from the top of an obstacle course across the way. There is also an outdoor theater, plenty of trails, gardens, and another playground for toddlers.
When we went, the Sakura trees provided a beautiful tunnel over the lower part of the rollerslide. It was a little hard to enjoy the beauty at mach-4.