Okutsu Valley (Okutsukei), Kagamino

Okutsu Valley (Okutsukei) stretches approximately 3 kilometers along the upper reaches of the Yoshii River in Okayama Prefecture. This natural gorge has been shaped over hundreds of thousands of years by water erosion carving through granite bedrock, creating a landscape of distinctive rock formations, waterfalls, and deep pools. The valley gained cultural recognition when it served as a filming location for the 1962 movie "Akitsu Onsen" starring actress Mariko Okada, and it continues to attract visitors seeking both natural beauty and connection to the area's hot spring heritage.

The valley's most significant geological feature is the Usubuchi Oketsu Group, considered the best collection of potholes in eastern Japan. These circular depressions were formed by pebbles rotated by water currents over tens of millions of years, creating what geologists consider academically valuable formations. The gorge is organized around eight scenic spots including Ishiwari-zakura (a cherry tree growing through split stone), Sasaketaki waterfall, Kotobuchi pool, and various rock formations. The name Kotobuchi reportedly derives from the koto harp-like sounds sometimes heard at the site.

Visitors can encounter well-maintained walking trails that run along both sides of the river, with the west bank trail extending from Otsuri Bridge to Kotobuchi, and the east bank path connecting Otsuri Onsen to the pothole information boards. The promenade includes sections with iron scaffolding attached to rock walls, allowing close observation of the geological formations. Visitors should wear appropriate walking shoes as the paths are unpaved. The nearby Otsuri Onsen hot spring area, located just minutes from the valley, offers day-use bathing facilities and has been valued since the Edo period for its beautifying mineral waters.

Admission to Okutsu Valley is free year-round. During the autumn foliage season, a shuttle bus operates from 9:30 AM to 4:00 PM at 30-minute intervals, costing 400 yen for adults and 200 yen for children for unlimited daily rides. Limited parking is available with space for approximately 10 vehicles. The valley is located in Kagamino Town, approximately 35 minutes by car from Mimasaka-Sendai Station.