We liked Tsugane Waterfall in Oseto so much that we visited it twice last week and we'll likely go back this week.
It's a beautiful waterfall in a beautiful location... not far from Yukinoura Beach. The first picture is from the lower falls and the second photo is what you find when you hike up the trail.
From the parking area, it a short 300 meter hike over a dam and through this tunnel. It is a very easy hike on a paved trail. The hike up to the upper falls is a little more rustic, though there is a bathroom along the way.