I went with a friend today to explore the area around my town and ended up at some waterfalls near a town called Maruseppu. The first waterfall we went to, Yamabiko Falls, was a quick five minute hike from the parking lot. Before we reached the water there was a torii gate and a small shrine where people could make offerings. The waterfall itself was about 28m tall with a Shinto shrine at its base. In Shinto religion they believe kami (spirits) live in nature so it's common to see shrines near waterfalls.