大隅半島と南方ルートの古代信仰The Osumi Peninsula and Ancient Faith on the Southern Route

Today I traveled south along the Osumi Peninsula, passing through Kagoshima and Miyazaki, tracing the remnants related to the mysterious southern routes of cultural transmission in ancient Japan. The Osumi Peninsula lies on the eastern side of southern Kyushu, and from ancient times, this entire region was home to significant tribes appearing in myths and traditions that remain unresolved. Their faith originates in the Jomon period. In other words, while northern and central Kyushu show a layering of culture through exchange via the Korean Peninsula that stands out more than the traces of the Jomon, in the south an older way of life kept a strong hold, and the people who lived there were able to preserve Jomon practices for a long period, making them vital figures in ancient Japanese history. However, the Jomon people of the Osumi Peninsula have rarely been investigated historically, and they remain extremely difficult to understand. From my visit this time, I would like to open a space for insight. The first place I visited was Tsuma Shrine.

This shrine is now written in kanji as 都萬, but in the past it was also written as 妻万, and it is said to have long been worshipped as “妻の宮.” Enshrined here is Konohanasakuya-hime, who became the principal consort of Ninigi, who descended from heaven (tenson korin, 天孫降臨), and bore him three children. Among them were Umisachihiko and Yamasachihiko, whom I mentioned yesterday. At that time, since breast milk alone was not sufficient, it is said that amazake was made and used in place of breast milk to raise the children. From then on, women who lacked sufficient milk after childbirth visited this shrine to pray, and old documents note that their milk would then flow, drawing faith from ancient times.

Looking at the location of the shrine against a topographical map, it becomes clear that it stands on ancient hill country, overlooking what was once a bay and wetlands. From the hill where the shrine is built, many ritual implements believed to date to the Yayoi period, such as mirrors, have been found, with 51 bronze mirrors unearthed. These relics convey the impression that the site prospered as a key point under the influence of Chinese dynasties. Though no trace of that landscape remains today, the fact that this hill overlooked a once deeply indented bay shows the faith of this shrine stretches back to very ancient times. Among the shrines of Hyuga Province (日向国), Tsuma Shrine was considered one of the most important, as it is said that shrines were founded in each of the five districts of Hyuga, even though its exact foundation date is unknown. This suggests that faith in Konohanasakuya-hime was rooted here from very early on.

Yet more important than Konohanasakuya-hime for understanding the faith of the Osumi Peninsula and Jomon tribes is Tsukuyomi Shrine (月読神社), located in a place with the unusual name Kushira (串良). Tsukuyomi (ツクヨミ) appears in Japanese mythology as one of the deities born from Izanagi along with Amaterasu and Susanoo, yet curiously descriptions of Tsukuyomi are extremely scarce, and shrines where he is worshipped as the principal deity are very limited nationwide. Considering how famous Amaterasu and Susanoo are, this scarcity hints at some significant ancient occurrence.

“Tsukuyomi” means “the deity who reads the moon,” suggesting that priestesses leading tribal groups may have worshipped this kami, interpreting the waxing and waning of the moon for agriculture and fishing, divining omens, and guiding responses. According to shrine records, this shrine was founded around the 15th century, but walking the terrain reveals it once stood on a small island within a bay, indicating that it was a vital sacred site for ancient tribes.

Even the name Kushira itself is meaningful. “Kushi” (櫛) refers to ritual and divinatory tools, combs believed to be used when offering prayers to the kami. The local fudoki (風土記) also mention the existence of specific groups that worshipped the “kami of Kushira.” In ancient times combs were magical tools used by priestesses to conduct divination and question the divine will, which they would then convey to male chieftains who governed politics. This hints at the tribal ritual system. Visiting in person, the island on which the shrine stands feels like an ancient burial mound, strongly suggesting the remnants of old ritual structures.

The deities enshrined here further convey traces of the ancient layer. The main enshrined deity is Tsukuyomi, but other kami related to rice cultivation are also present, showing a later association with rice agriculture that differs from the older stratum. What stands out, however, is the presence of Takeminakata and Yasakatome. Takeminakata, the son of Okuninushi of Izumo and Nunakawa-hime of Koshi (Hokuriku), is a vital deity of the Izumo lineage, and today he is worshipped as the principal kami of Suwa Taisha. Yasakatome is regarded as his wife, but this suggests she may originally have been a female chieftain of the local tribe before the arrival of the Izumo lineage.

In other words, Takeminakata of Izumo may have come to the Osumi Peninsula for territorial expansion and formed an alliance through marriage with Yasakatome, the local leader. Thus the early development of Tsukuyomi faith likely combined these tribal elements with guidance through lunar-based divination for agriculture and fishing, along with ritual practices using combs, clearly implying the presence of priestesses. Why Tsukuyomi appears in Japanese mythology as a peer of Amaterasu and Susanoo remains a puzzle, but a clue may lie in the Jomon tribes of the Osumi Peninsula later moving into the Kansai region and exerting strong influence. Those Jomon tribes based in Osumi were the Hayato.

The traces of the Hayato remain around Tsukuyomi Shrine, but they are complicated by the mixing of Jomon, Yayoi, and Kofun elements. Ideally, clarifying the tribal transitions of this region by era would lead to greater understanding of Yamato, but unfortunately this area has rarely drawn attention. The Osumi Peninsula contains countless kofun. For example, the Tsukazaki Kofun Group was built in the 4th–5th centuries and includes 54 round kofun, 5 keyhole-shaped tombs (前方後円墳), and 29 underground chamber tombs unique to southern Kyushu. These underground tombs are a distinctive Hayato burial style. Notably, the Osumi Peninsula is the southernmost region of Japan where keyhole-shaped tombs have been constructed, indicating that this area represented the southern limit of the kofun cultural sphere. Excavations have also yielded haniwa and sueki, advanced artifacts that later became central to the Yamato cultural zone.

Today the kofun area has been developed into farmland, but topographically it is clear that in ancient times the kofun were always built on prominent hilltops overlooking the indented bays of Shibushi Bay and Osumi Bay, suggesting boat travel was essential. The strategic siting of the kofun shows these were specially chosen places, key centers of their lives. Above all, the fact that keyhole-shaped tombs, haniwa, and sueki have been identified here at the southernmost edge of the Japanese archipelago is extremely important.

This points not only to migrants arriving via the Korean Peninsula, the prevailing theory, but also to the existence of migrants who came by southern sea routes—perhaps mixed communities from the Chinese coast, or unknown tribes traveling from Southeast Asia through the Ryukyu and Amami Islands to land sporadically in Japan.

Unfortunately, the Osumi Peninsula, which holds the key to unlocking the southern route of cultural transmission in ancient Japan, has hardly been investigated, and there have been few chances to study and retell it, leaving it a culture that is already being lost. The memory of the Hayato still breathes quietly beneath life in Osumi, but the places where it could be inherited and spoken have nearly vanished. Even while visiting shrines and kofun related to the Hayato, one strongly feels how seldom that memory comes to the surface.

Conversely, unless the southern route is clarified, Japanese history will remain fixated on the Korean Peninsula route and inevitably run into dead ends. Traveling across regions in search of ancient history, it becomes clear that such a limited view cannot be true. Will history that receives no light continue to be left behind, with everything buried? Or will a movement arise to shine light again on the memory of the Hayato that lives in this land and to deepen understanding? From my journey around the Osumi Peninsula, I felt that for now things lean toward the former. This is a consequence of modern homogenization, but the same situation applies not only to Osumi, but also to Tohoku.