小倉から門司港へ：関門海峡の玄関口From Kokura to Moji Port: The Gateway to the Kanmon Strait

Today, I have come from Kokura to Moji Port, the gateway to the Kanmon Strait that stretches between northern Kyushu and Shimonoseki in Yamaguchi Prefecture on Honshu. Seen in a wider scope, this region was the very first threshold for those arriving from the Korean Peninsula who wished to enter the Seto Inland Sea. Since ancient times, guarding this strait had been, for the local tribes, the front line that kept the flow of arrivals from reaching Yamato, where the imperial court was located, and the gateway through which passage was decided.

Because of this, Kokura and northern Kyushu as a whole, being port towns, have historically fostered people with a rough temperament yet also of remarkable gentleness, forming unique communities. Today, the Kanmon Bridge connects Shimonoseki and Kokura, making passage easy, but in the past the scenery was filled with countless ships constantly crossing back and forth. And to travel southward via Usa Jingu toward Hyuga in Miyazaki—the very rootland of Emperor Jinmu—it was necessary to cross this strait; failing that, one had to circle widely around through the Goto Islands and reach Kumamoto or Kagoshima. Then, what was the true ancient history of this region? Despite its role as the front line of defense for the Japanese archipelago, much about it remains shrouded in mystery compared to other regions.

One reason is that the geographical environment differed greatly between antiquity and the present. Much of northern Kyushu was once under the sea, and this continued from the Yayoi period through the Kofun period. Furthermore, northern Kyushu’s major entry points for migration from the Korean Peninsula—Itoshima in Fukuoka Prefecture and Karatsu in Saga Prefecture—were connected with the polities of Ito-koku and Matsuro-koku mentioned in the Wajinden, while scholars long maintained that no major powers existed in eastern northern Kyushu. However, walking the land makes it clear such a notion is untenable. From Shimonoseki to Kokura and Moji, tribes moved about since antiquity, something evident from the ancient shrines built along the coastline, just as at Izumo Taisha. In other words, this strait too was an important stronghold for seafaring tribes in transit.

Traces of this remain in place names. Inland from Kokura lies an old mountain-foot region called “Yamato” (山門, written with the characters for “mountain” and “gate”), which reveals intriguing history when examined closely. Conventionally, “Yamato” refers to the southern Nara Basin, considered the birthplace of the imperial court, but in fact the phonetic origin and place name may have come from northern Kyushu. Written as “山門” on the Kyushu side instead of “大和,” the characters symbolized the way mountains stood like gates enclosing an inlet, with the sea once reaching deep inland. This is exemplified by Mount Adachi and Mount Washimine at the southern edge of Kokura, forming a gate between which the Murasaki River still flows into the Kanmon Strait; it suggests this whole area was once a bay.

It is possible that a tribal group called Yamato, guardians of this gate, later migrated eastward and became the Yamato in the Nara Basin. This would mean this region was the starting point of Yamato and the homeland of tribes that went on to shape Japan.

Indeed, significant ruins have been unearthed in the Yamato heartland between these mountains. This is the Jono site, located on hills that once bordered the ancient bay. There, two stone coffins were found side by side on the hilltop, and notably, both were for children. They were not ordinary burials; grave goods and careful treatment suggested they were children related to royal succession in the region.

What is fascinating is that the two coffins were from different times, yet both contained children, one around four or five years old (the other’s bones remain unidentified). Both coffins had cinnabar about 1–2 cm thick inside, but analysis revealed it was not red ochre but mercury-based cinnabar. While red pigments had been used since the Jomon period, the sudden increase of cinnabar in Yayoi–Kofun burial practices indicates the influx of groups with different belief systems. Partial grave goods were also found, hinting—though not definitively—that these were descendants of the last royal line of the region, possibly heirs to authority. It is thought the two children may have been siblings, a fact with important implications for understanding the typical structures of Yayoi society.

Interestingly, during the latter half of the late Yayoi period, the local stronghold was slightly further south, but by the end of Yayoi it shifted northward to this area. This could mean that a fortress along the Suo-nada coast guarding the entrance to the Seto Inland Sea was captured and destroyed, marking the end of the Yayoi era here. The cause of the children’s deaths is uncertain, but one possibility is ritual sacrifice.

In fact, the discovery of multiple child burials together is rare nationwide, and I personally consider it possible that, faced with an upheaval bearing down on them, the Yayoi people offered these children as sacrifices to seek spiritual protection. With the fall of this region, Yayoi culture in northern Kyushu ended abruptly, ushering in the Kofun period. Power dynamics were swiftly redrawn, and this current flowed rapidly into the Yamato of the Nara Basin. Perhaps at this time, the old Yamato tribe abandoned this land and fled eastward to Nara.

Thus, the beginnings of Yamato may have been deeply tied to the collapse of this region. Why, then, has this history remained so unexplored? My private investigations suggest that the abrupt end of the Yayoi period is expressed in the mass burial of ritual items like bronze bells, symbols of their community. What, then, is the hidden history conveyed by the burial of these children?

Traces of a force and a violence unlike anything before, redrawing the map of power across the archipelago, are gradually emerging as I investigate sites across the land. But what was the dynamic behind them? By uncovering what the Yayoi people last witnessed, the deep mysteries of ancient Japanese history may enter an entirely new stage.