Hiki River Prefectural Natural Park is one of the outstanding natural areas of southern Wakayama Prefecture. Centered around the clear waters of the Hiki River and the beautiful valleys of the Kumano River (Iya-gawa), which rises around Mount Hyakkenzan, the park brings together rugged mountains, deep forests, clear streams, waterfalls, and peaceful rural landscapes.
Far from the noise of the city, the area offers a chance to experience the natural beauty of the Kii Peninsula throughout the year. Spring brings fresh green foliage, summer offers cool mountain streams, autumn transforms the forests with brilliant colors, and winter creates a quiet landscape surrounded by mountains.
The park is especially appealing to hikers, mountain climbers, photographers, and travelers who enjoy exploring Japan’s less crowded natural landscapes.
One of the park’s greatest attractions is Hyakkenzan Valley, which stretches along the southern foothills of Mount Hyakkenzan.
Over countless years, flowing water has carved the valley through the surrounding rock, creating a dramatic landscape filled with massive boulders, unusual rock formations, deep pools, and waterfalls of various sizes.
Following the trail through the valley, visitors encounter crystal-clear water flowing over rugged rock surfaces beneath a dense canopy of green. The atmosphere can feel almost otherworldly, particularly in places where the forest closes in around the stream.
The valley is also rich in deciduous broad-leaved trees, including horse chestnuts, Japanese bigleaf magnolias, stewartia, and Japanese maples. Their changing colors and foliage give the valley a different appearance with every season.
One of the notable sights in Hyakkenzan Valley is Umetaro Pool, a scenic area associated with a local legend.
Large Ubame oak trees, including one said to be approximately 500 years old, grow around the pool. The combination of the ancient tree and clear mountain stream creates a striking and mysterious scene.
According to local tradition, the name Umetaro comes from a woodcutter named Umetaro. It is said that a branch he dropped in the area took root and eventually grew into a great tree.
Whether viewed as folklore or as part of the cultural heritage of the valley, the story adds another layer of fascination to the landscape.
Located near the entrance to the valley, Umetaro Pool is also an inviting first stop for visitors beginning their exploration of Hyakkenzan Valley.
Beyond Umetaro Pool, enormous rocks appear to block the route ahead. However, a narrow opening between the rocks allows hikers to continue.
Stairs have been provided through the rocky passage, allowing visitors to move between the huge formations.
Walking through this section can feel like exploring a natural stone tunnel. It is one of the most memorable parts of the valley trail and offers an opportunity to experience the dramatic power of nature at close range.
Hyakkenzan Valley is particularly attractive to visitors who enjoy waterfalls. Several falls appear along the route, each with its own character and surrounding scenery.
After passing through the gap between the giant rocks, visitors reach Kayano Falls.
The waterfall descends in two stages, surrounded by lush greenery and clear flowing water. The combination of rock, forest, and falling water creates one of the characteristic landscapes of Hyakkenzan Valley.
Further along the trail is Ama-goi Falls, whose name means approximately “Rain-Prayer Falls.”
According to local tradition, rain-prayer kagura dances were performed here during periods of drought. Kagura is a traditional sacred dance performed in Shinto rituals, often as an offering to the deities.
The waterfall flows quietly through the forest, giving the area a particularly serene and sacred atmosphere. The combination of the isolated woodland and falling water also makes it an appealing spot for photography.
Beyond Ama-goi Falls are Sanjusan-biro no Tsubo, a deep natural pool, and Meoto Falls, or “Married Couple Falls.”
The surrounding rock formations and clear stream demonstrate how water has gradually shaped the valley over an immense span of time.
One of the most impressive waterfalls in Hyakkenzan Valley is Inuochi Falls.
The name is associated with a local story about a dog that accidentally fell from the waterfall while chasing a wild boar.
Today, the waterfall descends in a narrow white stream directly into its pool below, creating an elegant and almost mystical appearance.
A resting area nearby provides a convenient place to pause and enjoy the scenery before continuing along the trail.
Beyond Inuochi Falls, hikers eventually reach the trailhead for Mount Hyakkenzan.
From here, the route becomes a more demanding mountain hike. One of the highlights along the way is a scenic viewpoint known as Oiwa, or “Great Rock.”
From this point, hikers can enjoy views toward the surrounding mountains, including Mount Hoshiyama and Mount Nyudo. The open view provides an excellent opportunity to appreciate the scale of the Kumano mountain landscape.
After the viewpoint, the trail continues upward through areas of planted cedar and cypress forest. Some sections are steep, requiring appropriate footwear and a reasonable level of hiking preparation.
Reaching the summit, however, brings a rewarding sense of accomplishment. From around the summit area, hikers can see mountains such as Gonnyakuyama, Notakehoji, Hoshiyama, and Nyudo-yama, offering a broad view of the rugged landscape of the Kii Mountains.
Another must-see attraction in the park is Yakusa Falls, one of the waterfalls selected for Japan’s celebrated “100 Best Waterfalls” list.
Located along the middle reaches of the Hiki River, the waterfall plunges approximately 22 meters down a mountainside.
Its appearance changes dramatically depending on the amount of rainfall. After heavy rain, the flow can become particularly powerful, while during drier periods it may appear much more delicate. This variability has earned Yakusa Falls the nickname “the Phantom Waterfall.”
When sunlight enters the mist rising from the waterfall, a rainbow can sometimes appear in the spray, producing an enchanting scene in which the water seems to shimmer with multiple colors.
The surrounding landscape is especially beautiful during the fresh greenery of early summer and when mountain cherry blossoms add touches of color in spring.
These seasonal changes make Yakusa Falls a popular destination for photographers and nature lovers.
The Hiki River forms one of the central natural features of the park. Because of its exceptionally clear water, it is sometimes described as the “last clear stream of the Kii Peninsula.”
The river rises in the mountains of Kumano and supports a rich aquatic ecosystem. Fish such as ayu sweetfish, amago trout, and eel inhabit its waters.
Every year around late May, the ayu fishing season opens, attracting anglers from Wakayama and other parts of Japan.
Even for visitors who are not interested in fishing, the river is an enjoyable place to appreciate the scenery. Walking beside the clear water and listening to the sound of the current provides a simple way to experience the peaceful character of the region.
Another beautiful area within the park is Yasukawa Valley, where visitors can enjoy different outdoor experiences throughout the year.
In spring, the mountains offer opportunities to observe and collect edible wild plants. Summer is ideal for enjoying the cool streams and fishing. Autumn brings colorful foliage, while winter offers a quiet setting for hiking.
Autumn is particularly impressive. Bright red Japanese maple leaves are reflected in the flowing water, creating a vivid contrast between the colorful forest and the clear mountain stream.
For many visitors, one of the best times to explore Hiki River Prefectural Natural Park is from late April to mid-May, when the mountains are covered in fresh green foliage.
The brilliant new leaves create a beautiful contrast with the clear streams and dark rock formations of the valleys.
Late May is also an attractive period, when rhododendrons bloom across the mountains.
For autumn scenery, the recommended period is generally from late November to early December. During this season, the mountainsides and valleys can be transformed into a spectacular combination of red, orange, and yellow foliage.
Hiki River Prefectural Natural Park offers much more than beautiful scenery. Its valleys, waterfalls, rivers, forests, and mountains are accompanied by local legends and stories that have been passed down through generations.
The mysterious Umetaro Pool, the rock passages of Hyakkenzan Valley, the series of waterfalls, the challenging hike to Mount Hyakkenzan, and the spectacular Yakusa Falls each offer a different way to experience the natural environment of southern Wakayama.
The clear waters of the Hiki River and the peaceful rural landscapes surrounding the park also provide a glimpse into the traditional relationship between local communities and the mountains and rivers of the Kii Peninsula.
For travelers seeking an authentic encounter with the wild beauty of southern Japan, Hiki River Prefectural Natural Park is a rewarding destination. Take time to walk through the forests, listen to the sound of mountain streams, discover waterfalls hidden among giant rocks, and appreciate the changing scenery of the Kumano mountains.