It follows generally a southeastern and southern course to exit into the Sagami River at the Uenohara town.

Nagasaku (長作), Saihara (西原), Yuzurihara (棡原) and another small villages scatter along it.

Biodiversity is well preserved due to mountain wood and the lack of dam development.

Many species of upper stream fish in Japan live; White-spotted Char (Salvelinus leucomaenis), Seema (Oncorhynchus masou), Japanese Fluvial Sculpin (Cottus pollux), Ayu (Plecoglossus altivelis), Amur Minnow (Rhynchocypris lagowskii), Pale Chub (Zacco platypus) and others.

Also Forest Green Tree Frog (Rhacophorus arboreus) and Japanese clawed salamander (Onychodactylus japonicus) inhabit this river.