The head of the Nonogawa River is a hot spring flowing into a large depression the locals call the Dragon's Bathtub before spilling over the side of the mountain Myouyama-san and into the valley.
Flora & FaunaA rumor says someone tried to catch one of the creatures. How a spirit rose and lead the wildlife to kill the man is a common summer night's ghost story. They say the ghost's repentance is to protect the area and warn any fools who would harm the area or its inhabitants. Hikers who camp near there overnight reported hearing footsteps and murmuring at about 2 AM. There used to be another path, but a landslide took out the path on the side facing Nonogawa.
You're Kidding Me! There Weren't Seahorses!
Contrary to what most texts on seahorses will tell you, there were indeed baby ones in this stream, not pipefish. Photographic proof exists of palm sized ones, from 100 years ago. The documentation claims they were iridescent blue. Shortly after that, they disappeared. Though what happened shortly after their discovery, no one knows. Perhaps they followed the river to the sea? (In Japanese myths, they consider seahorses to be baby dragons.)
This is Shion's territory. So I'm sure you can put two and two together. ;)