Jōshinzuka Tomb

Joshinzuka Kofun: A Quiet Square Tumulus with an Extraordinary Story

Tucked away among the fields of Kamisanzai in Saito City, Miyazaki Prefecture, the Joshinzuka Kofun (常心塚古墳) is the kind of place that rewards travelers who venture beyond the usual sightseeing routes. Although it lies only seven kilometers southwest of the famous Saitobaru Burial Mounds, this small but architecturally remarkable burial mound stands alone in a quiet agricultural landscape, almost untouched by modern development. Its near-perfect rectangular form, surrounded by a moat and outer embankment, makes it one of the most evocative examples of terminal Kofun-period architecture in southern Japan—and one of just four tumuli of its kind in the entire country.

Beyond its archaeological importance, Joshinzuka Kofun carries a haunting Edo-period legend that gives the site its name: that of a Buddhist monk named Joshin, who is said to have entered the burial chamber and quietly passed away there in deep meditation. For modern visitors, the result is a layered experience: an ancient tomb, a folk memorial, and a peaceful rural vista all in one place.

The Setting: A Plateau Above the Sanzai River

Joshinzuka Kofun sits on the southwestern edge of the Azukino Plateau (also called the Joshinbara Plateau), at an elevation of roughly 60 to 65 meters above sea level, overlooking the left bank of the Sanzai River. The plateau is now given over to fields and farmland, but the kofun rises distinctly above the surrounding crops, visible from quite a distance.

This part of central Miyazaki was once a thriving center of ancient power in southern Kyushu. The famous Saitobaru Kofun Cluster to the northeast contains more than three hundred tumuli built between the late third and early seventh centuries. Joshinzuka stands apart from that cluster, however, both physically and typologically—a solitary square tomb in a landscape otherwise dominated by round and keyhole-shaped mounds.

A Late-Period Square Tomb: Architecture and Dimensions

Joshinzuka is classified as a "hōfun" (方墳), or square tumulus, with sides oriented almost exactly to the cardinal directions. The mound itself measures approximately 25 meters north-to-south and 23.8 meters east-to-west, rising to a height of about 3.3 meters. It is thought to have been built in two or three terraced tiers, although portions have been worn down by centuries of weather and human activity.

The mound is encircled by a moat about two meters wide and a substantial outer embankment that survives almost intact. Including this embankment, the entire monument measures roughly 40 meters north-to-south by 37.5 meters east-to-west—a clear, geometric footprint that becomes especially striking when viewed from above. A further outer ditch was discovered just outside the embankment during a 2002 survey, when the Saito City Board of Education conducted a partial investigation in conjunction with prefectural agricultural road improvements.

The interior burial facility has never been fully excavated. However, a portion of stones believed to belong to a stone chamber is exposed near the rear of a small shrine on top of the mound, and researchers strongly suspect that the burial chamber is a "yokoana-shiki sekishitsu" (横穴式石室)—a corridor-style stone chamber with a horizontal lateral entrance, a form imported from the Korean peninsula that became common across Japan in the late sixth and seventh centuries.

Why Joshinzuka Was Designated a National Historic Site

Joshinzuka Kofun was designated a National Historic Site of Japan on March 24, 1980. The reasons for this honor go beyond its picturesque condition.

First, the kofun is an exceptional example of late- or terminal-period (7th century) tomb architecture in southern Kyushu. By this time, the construction of massive keyhole-shaped tumuli had ended, and regional chieftains were instead being buried in large round or square mounds equipped with stone chambers. Joshinzuka's dimensions, careful orientation, and well-preserved earthworks make it a textbook example of this shift.

Second, and perhaps even more remarkably, Joshinzuka belongs to a tiny family of tombs known informally as "Ishibutai-style" tumuli—square or near-square tombs surrounded by an outer embankment, named after the famous Ishibutai Kofun in Asuka Village, Nara Prefecture. Only four such tumuli are known in all of Japan: Ishibutai itself (traditionally associated with Soga no Umako), the Yōmei Emperor's tomb in Osaka, the Oni-no-Iwaya Kofun in the nearby Saitobaru cluster, and Joshinzuka. That two of these four lie within a few kilometers of each other in Saito City strongly suggests close ties between the local chieftains and the central Yamato court during the formative years of the Japanese state.

Third, the surrounding area contains the Joshinbara underground tunnel tombs (常心原地下式横穴墓群), a group of at least eight subterranean burial chambers dating from the late fifth to early seventh century—a tomb style unique to southern Kyushu. These tombs likely belonged to the ancestors or social group of whoever was eventually interred in Joshinzuka, giving the site a layered story about the evolution of local burial practices over two centuries.

Highlights and What to See on Site

Joshinzuka Kofun is not a manicured park—it is a working archaeological landscape, surrounded by farmland with an explanatory signboard installed by the Saito City Board of Education. That said, several features make a visit memorable.

• The clean square outline of the mound and its surrounding embankment are unusually well-preserved, allowing visitors to grasp the geometry of a 1,400-year-old burial site at a glance.
• A small wooden shrine (祠堂) sits atop the mound, with a flight of stone steps leading up to it. The shrine commemorates the monk Joshin and was built by villagers in later centuries.
• Near the rear of the shrine, a few exposed stones hint at the unexcavated burial chamber below.
• The surrounding fields offer wide, open views and a peaceful rural atmosphere—particularly beautiful in early morning light or at sunset.
• The detailed on-site signboard, installed by the local board of education, was inspired in part by research conducted by sixth-grade students at Sanzai Elementary School, who studied the site as part of a local heritage project.

The Legend of the Monk Joshin

The kofun takes its name not from any ancient occupant but from a monk who is said to have lived during the Edo period. According to local tradition recorded in the 1884 work "Hyūga Chishi" (a regional gazetteer of Hyūga Province), a monk named Joshin from the temple Fukuō-ji in Kamisanzai sensed that the end of his life was near. He is said to have dug a pit on the burial mound, entered it, and continued chanting sutras until he passed away in meditation—a practice associated with "sokushinbutsu" (即身成仏), or the attempt to achieve buddhahood through self-mummification.

Whether the story is literal history or local folklore, it has shaped the way the community remembers the site. Villagers built a small shrine to honor him, and the burial mound itself came to bear his name. Today, the legend gives Joshinzuka a unique double identity—a prehistoric tomb and a memorial to a much later spiritual seeker layered into a single landscape.

Nearby Attractions and Surrounding Area

A visit to Joshinzuka pairs beautifully with several nearby sites that together form one of Japan's richest concentrations of Kofun-period heritage.

• Saitobaru Burial Mounds (Special National Historic Site): About seven kilometers to the northeast, this vast plateau holds over 300 tumuli, including the enormous Mesahozuka and Osahozuka mounds and the unusual Oni-no-Iwaya Kofun—another "Ishibutai-style" tomb closely related to Joshinzuka.
• Miyazaki Prefectural Saitobaru Archaeological Museum: A modern, free-to-enter museum dedicated to the archaeology of Miyazaki, with extensive displays of haniwa, weapons, and reconstructed burial chambers.
• Tsuma Shrine: Dedicated to Konohanasakuya-hime, a goddess from the ancient Japanese creation myths recorded in the Kojiki and Nihon Shoki.
• Kiki no Michi Walking Path: A roughly four-kilometer trail through the Saitobaru area that links sites connected to the Hyuga myth cycle.
• Seasonal flower fields: In spring, cherry blossoms and rape blossoms; in summer, sunflowers; in autumn, cosmos blanket the Saitobaru landscape.