Higashi-Sankei

Higashi Sankei Prefectural Natural Park is a protected natural area spanning parts of Tokushima City, Anan City, Katsuura Town, Sanagōchi Village, Kamiyama Town, and Naka Town in eastern Tokushima Prefecture on Shikoku Island, Japan. ^[1] The park protects an inland mountainous landscape centered on Mount Nakatsumine, the Hata Five Falls, and the Saga Gorge — it does not front the Kii Channel or any coastline. ^[2][3] It was designated a Tokushima Prefectural Natural Park on December 27, 1966, effective January 1, 1967, under Japan's Natural Parks Act, and covers 44.32 km². ^[1][3] The park also contains two temples on the 88-temple Shikoku pilgrimage route, Kakurin-ji (Temple 20) and Tairyū-ji (Temple 21), and the ruins of Ichinomiya Castle. ^[3][4] Its relatively accessible location near the prefectural capital makes it a popular destination for residents of Tokushima city seeking forested mountain scenery within a short drive of the urban center.

The park supports wildlife representative of the warm-temperate mountain forests of inland eastern Shikoku. Japanese serow inhabit the steeper slopes of Mount Nakatsumine, while Japanese raccoon dogs and red foxes range through valley margins and woodland edges. Avifauna includes resident species such as Japanese pygmy woodpeckers, varied tits, and bush warblers. The park's stream ecosystems, part of the Naka River system, harbor native freshwater fish including ayu sweetfish. ^[1]

Vegetation across Higashi Sankei reflects the warm-temperate climatic zone of inland eastern Shikoku, with broadleaf evergreen and mixed forest covering the slopes of Mount Nakatsumine and the Saga Gorge. Ferns and mosses cover shaded rock faces along the gorge, sustained by the valley's consistently moist microclimate. Seasonal wildflowers, including azalea, provide notable spring color along the park's trails, while maple and oak contribute to autumn foliage displays in the valley forest sections.

Higashi Sankei's terrain is defined by the mountainous interior of eastern Tokushima rather than by a coastline; the park does not include any shoreline along the Kii Channel. ^[1] Its most prominent landform is Mount Nakatsumine, at 773 meters the highest peak within Tokushima City, where rivers have cut the Saga Gorge, a valley within the Naka River system. ^[2][1] The Naka River itself, which borders part of the park, is designated a Class A (first-class) river under Japanese river law. ^[1]

Higashi Sankei experiences a humid subtropical climate typical of inland eastern Tokushima Prefecture; unlike coastal parts of the prefecture, it is not directly exposed to the Kii Channel. Summers are hot and humid, with temperatures frequently exceeding 30 degrees Celsius in the valleys. A pronounced rainy season affects the region in June and July, followed by typhoon-related rainfall in late summer and early autumn, consistent with the wider Shikoku climate pattern. Winters are mild by Japanese standards at lower elevations, though the higher slopes of Mount Nakatsumine see cooler temperatures and occasional light snow. Spring and autumn offer the most favorable conditions for outdoor activities, with moderate temperatures and clearer skies between the main precipitation seasons.

The ruins of Ichinomiya Castle, overlooking the Ai River within the park, mark a site built in 1338 by Ogasawara Nagamune, a descendant of the Awa provincial military governor, and held for generations afterward by his descendants, the Ichinomiya clan. ^[1] During the Sengoku period the castle changed hands between the Hosokawa, Miyoshi, and Chōsokabe clans; after Toyotomi Hideyoshi's 1585 conquest of Shikoku, Hachisuka Iemasa occupied it as a base for ruling Awa Province. ^[1] Centered on a main keep at 144 meters elevation, the ruins were designated a Tokushima Prefectural Historic Site in 1954 and are the largest surviving mountain-castle remains in the prefecture. ^[1] The park also preserves sections of the Awa Henro-michi, the historic pilgrimage road linking Kakurin-ji and Tairyū-ji, designated a National Historic Site in 2010 and expanded in 2013 to add the Iwaya-michi extension; the route retains boat-shaped stone milestones and pilgrim grave markers documenting centuries of Shikoku pilgrimage traffic. ^[2]

Higashi Sankei was designated a Tokushima Prefectural Natural Park on December 27, 1966, effective January 1, 1967, under the framework of Japan's 1957 Natural Parks Act, which allows prefectural governments to protect landscapes of regional — as opposed to national — significance. ^[1] The park's boundaries cover portions of Tokushima City, Anan City, Katsuura Town, Sanagōchi Village, Kamiyama Town, and Naka Town. ^[1] Its designation reflects the prefecture's effort to conserve the forested mountains, gorges, and historic pilgrimage routes of the Naka and Katsuura river valleys inland from Tokushima city, not any coastal habitat. ^[2] The prefectural ordinance establishing the park has been amended repeatedly through 2024 while retaining its original boundaries. ^[1] Management responsibilities rest with the Tokushima Prefectural Government, which coordinates zoning and trail maintenance with the bordering municipalities.

The park's principal hiking route climbs Mount Nakatsumine, at 773 meters the highest peak within Tokushima City, with panoramic views over the surrounding mountains of the Katsuura and Naka valleys. ^[1][2] The Hata Five Falls, a group of five cascades in the upper Hata River, and the Saga Gorge are notable natural attractions within the park. ^[3][2] Cultural attractions include Kakurin-ji (Temple 20) and Tairyū-ji (Temple 21) on the Shikoku 88-temple pilgrimage, connected by the historic Awa Henro-michi pilgrimage road, and the ruins of Ichinomiya Castle. ^[3][4][5] Seasonal attractions include spring azalea blooms on lower slopes and autumn foliage of maple and oak in the gorge forest.

Access to Higashi Sankei is primarily by private vehicle via prefectural and municipal roads connecting Tokushima city with the inland towns of Katsuura, Sanagōchi, Kamiyama, Naka, and Anan that border the park. Parking areas serve key trailheads, including access to Mount Nakatsumine and the temple pilgrimage route. Basic visitor facilities including restrooms and information signage are present at principal entry points, though the park does not maintain a dedicated visitor center. Accommodation options are concentrated in Tokushima city and the surrounding towns rather than within the park boundary itself. Visitors are advised to carry sufficient water and provisions, as facilities within the park interior are limited. The proximity of the park to Tokushima city makes it feasible as a day trip from the prefectural capital.

Prefectural natural park status gives Higashi Sankei formal land-use controls that restrict development within designated zones, protecting the forested slopes of Mount Nakatsumine, the Saga Gorge, and the Naka River corridor from fragmentation by roads and residential construction. Conservation priorities include maintaining forest cover on the mountain slopes and sustaining water quality in rivers that support ayu and other native freshwater species. ^[1] The park's cultural heritage sites — the Awa Henro-michi National Historic Site and the Ichinomiya Castle ruins — receive separate preservation attention from Tokushima Prefecture and Tokushima City alongside the park's natural-area protections. ^[2][3]