Harajiri Falls (Oita prefecture) have been reviewed with nice information here (Harajiri Falls 2013) and since it is quite some time ago and I visited recently decided to update.
Coming by car you will probably park at the restaurants parking lot which is quite large and from there a nice path will take you to the falls. It is worth checking the farmers market for all the different kinds of local products. Decided to start by crossing the suspension bridge to get a view of the falls from afar. The beautiful horseshoe-shaped 20 meters high falls were a pleasure for the eye. The suspension bridge jolts quite a lot, especially if there are a few people on it, adding on the experience.
Crossing the bridge you can follow the circular path which will take you above the falls, with a few nice views on the way. On top of the falls there are no restrictions as to where you can go so you can actually go very much to the edge, being very careful of course. Afterwards you will pass by a watermill and then some stairs will take you down to the falls basin, no swimming allowed.
Viewing the falls from the bridge, the eastern part of the circular path and from the top is certainly beautiful but it is only until you get down to their basin for you to get the majestic feeling. Surrounded by the falls, with the sound of the tumbling water and the mist on my skin, I was mesmerized.
Instead of taking the stairs up you can follow a path under the suspension bridge which leads back to the restaurants parking lot. I really enjoyed that short walk back, not only because it was beautiful but also because I was the only person there.
The closest train station is Ogata station in the JR Hohi line. Coming from Oita is alright but not from Kumamoto as part of the line was damaged due to the earthquake in 2016. From Ogata station the falls are a bit less than 3km which you can walk or take a taxi.