山鹿に残る古代の弔いAncient Burial Traditions of Yamaga

Today, I traveled through Yamaga City in Kumamoto Prefecture. Yamaga is a minor region almost unknown even among Japanese people, yet for those interested in archaeology and ancient Japanese history, it is a remarkable place. Situated in the fertile basin of the Kikuchi River and surrounded by hills, the area gradually became inhabited from the Paleolithic period, with communities forming and evolving uniquely over time. At the same time, this area was affected by volcanic activity from Mount Aso, so the cultural developments of the Jomon and Yayoi periods flourished not here but rather in the northern coastal regions, such as Ito-koku and Matsuro-koku, and around the Yoshinogari site. For this reason, Yamaga has not received much attention.

However, as the Yoshinogari era drew to a close, a new power rose out of exchange with East Asia, and a profound change came to Kyushu, the front line of the Japanese archipelago. The age that later gave rise to what we now call the Kofun period brought new technologies, iron weapons and horses carried by ship in iron gear, and a shift in the balance of forces that the social order of the Jomon and Yayoi could no longer answer. As a result, instead of the northern coastal areas that became fierce battlegrounds, regions such as Yamaga emerged as centers of development.

The Kikuchi River, which flows into the junction of the Ariake and Shimabara Bays, runs upstream toward Tamana City and Yamaga City. Here, a rising power in search of an ideal new land thrived. Over the earlier Jomon and Yayoi way of life, the cultivated areas were converted into wet rice fields, and kingdoms centered on kingship took shape.

This is why Yamaga contains countless kofun (ancient burial mounds). Today I visited more than a dozen of them: some stand atop mountain ridges as the oldest tombs of Yamaga, while others, such as large keyhole-shaped tombs (前方後円墳) surrounded by clusters of smaller round tombs, spread across the hills, all reflecting complex forms of faith. It is clear that those known as kofun people were themselves divided into multiple lineages.

Among them, decorated kofun (装飾古墳), found throughout western Japan, are particularly concentrated here. Decorated kofun are tombs whose interiors are adorned with painted designs and colorful motifs. Yamaga has an especially high density of these sites. Yet due to damage from the Kumamoto earthquake, many have collapsed, and they are rarely open to the public. Instead, precise replicas in nearby museums reveal designs that are unmistakably continental in sensibility, utterly different from Jomon or Yayoi aesthetics.

As I toured these tombs, it became clear that the culture spreading from Tamana to Yamaga bore traits different from those of the earlier Jomon and Yayoi. Its colors, patterns, and ritual practices diverged greatly from Jomon and Yayoi traditions, and its funeral rites and ancestor worship display strikingly distinct forms, a measure of how great the change was. Much like Yoshinogari, which suggested reverence toward the north, several of these kofun clusters were built facing northward, indicating directional symbolism in their belief systems.

Today the region is largely depopulated, with abandoned fields spreading across the hills. Yet surrounded by mountains, the land offers open views, likely ideal for observing the sun’s movement. At the same time, one must consider that the immigrant tribes arriving via the Ariake Bay carried maritime symbols yet settled inland, adapting their lives to the land while retaining oceanic imagery.

Indeed, multiple boat images are painted inside decorated kofun, showing how deeply their culture was tied to a world beyond the sea. The area also evokes a curious sensation at shrines, where one feels it is somehow a foreign land beyond the frame of Japan, emanating a unique energy rarely found elsewhere in the country.

Perhaps the most remarkable feature of this region, even more than decorated kofun, is the presence of yokoana tombs (横穴墓). These were burial chambers dug into rocky hillsides, hidden from plain sight, where the dead were interred. This practice reflects ancient southern customs and was common along the Kikuchi River basin. Notably, the groups who built these tombs shared roots with those constructing kofun but later diverged into their own historical trajectory. Many of these graves employed boat-shaped stone coffins, a style known as shuso (舟葬), or boat burial.

Even today, faint traces of colorful pigments remain on the exterior walls of these horizontal tombs, showing how they once bore vivid decorations. These interactions and blends with completely different cultural spheres may well have sown the seeds of what later became a distinctly Japanese aesthetic sense.

Now I have arrived at Oita Station, where a fireworks festival is taking place. Fireworks blossomed in the night sky, signaling the end of summer at the close of August. Yet I wonder, has this disastrous summer truly come to an end? Forecasts warn that severe heat may last another month or two. More importantly, tomorrow marks the two hundred tenth day (nihyakutoka, 二百十日), which traditionally signals the onset of the typhoon season. Each year, more regions become inaccessible due to storms and torrential rains, and perhaps this year too, somewhere will once again face such devastation.