Learning from the Past (103) Kogoishi-style Mountain Castles, Emperor Keiko, Goshogadani Kogoishi, Mount of Saint Michael, Zo-yama Kogoishi, Lato Ruins, Empress Jingu, Mt. Kora Kogoishi, Mt. Raizan Kogoishi, Kinojo Castle Ruins, Eino-san Castle Ruins, Ishigajo-san Kogoishi, Mount of Saint Michael

Kogoishi-style Mountain Castles and Korean-style Mountain Castles
Looking at the distribution map of ancient mountain castles, there are Kinojo Castle, presumed to be the castle of Prince Homudamawaka and other Kogoishi-style mountain castles distributed from northern Kyushu to Okayama, as well as Korean-style mountain castles distributed from northern Kyushu to Ikoma in Nara. Mt. Kora Kogoishi (Kurume City, Fukuoka Prefecture) and Zo-yama Kogoishi (Miyama City, Fukuoka Prefecture) were reported by Shojiro Kobayashi during the Meiji era, and subsequently, the ruins of Mt. Raizan Kogoishi (Tsuiki) also became known1). Within the castle grounds of Zo-yama Kogoishi, there is the Yamauchi Kofun cluster dating to the latter half of the 6th century, and two bronze spears were excavated from the middle of Mt. Zo. By 1945, the Kogoishi of Mt. Raizan, Ishigajo-san, and Kage-uma were designated as historic sites, and in the 1950s, the Kogoishi of Goshogadani, Mt. Kora, Zo-yama, and Obikuma-yama were also designated.

Goshogadani Kogoishi and Emperor Keiko
Goshogadani Kogoishi (Yukuhashi City and Miyako Town, Kyoto District, Fukuoka Prefecture) has a place name "Goshogadani" (Valley of the Imperial Palace), which stems from the tradition that the 12th Emperor Keiko, who visited Kyushu, established an Angu (temporary imperial palace) here, and Keiko Shrine is enshrined within the castle1). The line connecting Uetsukiderayama Kofun, presumed to be the mausoleum of Emperor Keiko in Shoo Town, Katsuta District, Okayama Prefecture, and Goshogadani Kogoishi intersects almost at a right angle with the line connecting Tenman Shrine in Furazu, Yura, Tsukumi City, where Emperor Keiko's Hinashiro Palace is presumed to have been and the Mount of Saint Michael (Figure 1). This line is thought to connect Emperor Keiko's mausoleum and his palace.

Kurumazuka Kofun in the Isohama Kofun cluster, presumed to be the mausoleum of Emperor Keiko's consort, Yasakairihime-no-Mikoto (Oarai Town, Ibaraki Prefecture) and the line connecting to Goshogadani Kogoishi intersects almost at a right angle with the line connecting Ryugu Sogu Shrine (Anan City, Tokushima Prefecture), which passes near Uetsukiderayama Kofun, and the Faroe Islands (Figure 2). This line is consistent with the presumption that Uetsukiderayama Kofun is the mausoleum of Emperor Keiko and Kurumazuka Kofun (Oarai Town) is the mausoleum of Yasakairihime-no-Mikoto.

Zo-yama Kogoishi, Mt. Kora Kogoishi, Mt. Raizan Kogoishi
Since Japanese pyramids are on ley lines, I investigated whether Kogoishi-style mountain castles were also on ley lines. The line connecting Goshogadani Kogoishi and Zo-yama Kogoishi intersects almost at a right angle with the line connecting Mt. Kanou (Hinokage Town, Nishiusuki District, Miyazaki Prefecture) and the Ancient City of Lato in Crete, which is thought to be named after the goddess Leto, mother of Artemis, and near the latter line are Mt. Kora Kogoishi (Kurume City, Fukuoka Prefecture) and Mt. Raizan Kogoishi (Itoshima City) (Figure 3). Near the line connecting Mt. Kanou and the Lato ruins are Kora Taisha Shrine (Kurume City) and Raizan Sennyoji Daihioin Temple (Itoshima City) (Figure 4), and the "Raizan Sennyoji Engi" records that Empress Jingu prayed for the defeat of the enemy to the main deity of Mt. Raizan, "Sui-ka Raiden-shin" (Water-Fire-Thunder-Lightning Deity), before her overseas expedition.

The line connecting Tenman Shrine (Fukurato, Yura, Tsukumi City, Oita Prefecture), where it is estimated that Emperor Keiko's Hishiro Palace was located and the Lato ruins on Crete, and the line connecting Beppu Hachimangu Shrine (Sanyo-Onoda City, Yamaguchi Prefecture) and Meguri Kogoishi intersect near Goshogadani Kogoishi (Figure 5). This line is consistent with the tradition that Goshogadani Kogoishi was the temporary palace of Emperor Keiko.

Korasan Kogoishi and Empress Jingu
The line connecting the Kinojo Castle ruins, estimated to have been the castle of Prince Homutamawaka (top photo) and Korasan Kogoishi intersects almost at a right angle with the line connecting Einozan Castle ruins (Saijo City, Ehime Prefecture) and Mount Saint Michael, and passes near Iwashiro-yama Kogoishi (Hikari City, Yamaguchi Prefecture) (Figure 6). From this line, it is estimated that the Kinojo Castle ruins and Korasan Kogoishi are related. It is thought that Korasan Kogoishi was built at the end of the 4th century by Empress Jingu, estimated to be the consort of Prince Homutamawaka, to pray for victory for the dispatch of troops to Korea to Yamato-totohi-momoso-hime-no-mikoto, who is estimated to be enshrined at Kora Taisha Shrine.

Korean-style Mountain Castles
While there are no records of the construction of Kinojo Castle, there are records that Baekje officials and generals who defected and came from Baekje were dispatched for the construction of Nagato Castle, a Korean-style mountain castle 2), and the Nihon Shoki records, "Build Takayasu Castle in Yamato Province, Yashima Castle in Yamada District, Sanuki Province, and Kaneda Castle in Tsushima Province." Kikuchi District in Kumamoto Prefecture (Higo Province) Kikuchi District is written as " Kukuchi " in the Wamyō Ruijushō, and since it was initially read as "kukuchi," it is estimated that it was originally related to Susanoo-no-Mikoto. In the Battle of Baekgang in 663, the Wa state was heavily defeated by the allied forces of Tang and Silla, but Kikuchi Castle (Kikuchi-jo) is an ancient Korean-style mountain castle, estimated to have been built at the end of the 7th century, and from its location, it is also thought to have been intended to counter the Hi-no-Kimi, a powerful clan that held power in the Higo region, or the Hayato people of southern Kyushu.

References
1) Shin-Kodaishi no Kai (Ed.) 2025 "Learning Japanese Ancient History by Walking 2: The Establishment of the Ritsuryo State and the Tenpyo Era" Yoshikawa Kobunkan 2) Teiji Kadowaki 1992 "Ancient History of Kibi" NHK Books