Yatsumen-yama Mica Mine Remains

Yatsuomo-yama consists of the 67.4 m Otoko-yama (Male Mountain) and the 39 m Onna-yama (Female Mountain). Otoko-yama has been known as a mica (unmo / kirara) mining site since ancient times, and an entry in Shoku Nihongi dated the 7th day of the 5th month of Wadō 6 (713 CE) records that 'Yamato and Mikawa provinces were ordered to present mica.' Wakan Sansai Zue also records that 'mica comes abundantly and well from the Mica Mountain in Mikawa Province,' confirming that high-quality mica was produced here from antiquity. During the Edo period, mica was a monopoly product of the Nishio Domain and was actively shipped to Kyoto for use as a decorative material for folding screens and sliding doors. It was also exported overseas during the Meiji period, but mining was halted following a collapse accident in 1900 (Meiji 33), and in 1931 (Showa 6), after a schoolchild fell into an abandoned mine shaft, local youth groups filled in 642 of the mine shafts. One shaft was preserved as a cultural property. Nishio City Official 'Yatsuomo-yama Mica Mine', Wikipedia 'Yatsuomo-yama'.

The word 'kirara' appears in the early Heian medical text Daidō Ruijuhō as 'kirararyaku' (mica medicine), indicating that mica was also valued as a medicinal substance. Regarding the connection with the Man'yōshū: there is a local tradition claiming a poem about 'kirara staining robes' was composed here (unverified information). However, a search of the Man'yōshū database did not confirm a poem number explicitly identifying 'Yatsuomoyama' or 'Mikawa mica' as its subject; this connection may be cited in local histories but is treated here as unverified information. The derivation of the estate name 'Kira-no-Shō' (吉良荘) from the sound of 'kirara' (mica) appears in multiple historical sources and is generally accepted. Nishio City Official 'Kumaku Shrine'.

Yatsuomo-yama is a symbolic hill of Nishio City, and the summit observation deck of Otoko-yama commands a panoramic view of the Nishio city area. Onna-yama is cherished by local residents as a famous spot for cherry blossoms. Kumaku Shrine holds a Gozutenno deity figure from the Heian period and a ceramic komainu (guardian dog) from the Muromachi period (both Aichi Prefecture-designated Cultural Properties), but these are not on public display. A 'Mica Mountain Stele' (mica-mining record poem in Chinese characters) erected in Bunsei 10 (1827) by Matsuzaki Mei, a physician of the Nishio Domain, survives to the south of the Kumaku Shrine worship hall, engraving the history of mining in stone. FNN Prime Online 'Yatsuomoyama' (October 2023).

Spring (April) is the peak cherry blossom season on Onna-yama Park. The mine ruin and shrine can be visited year-round. The observation deck offers the clearest long-distance views on sunny mornings.

The surviving mica mine shaft is located behind a large information board and can be photographed through the iron grille. A composition combining the Kumaku Shrine main hall with the surrounding trees conveys the site's historical atmosphere.

The surviving mine shaft is sealed with an iron grille; entry is not possible. The mountain path around Kumaku Shrine is generally maintained, but some slopes are unpaved. Do not enter private land without permission. Access to the mine ruin should be made via public roads and designated walking paths.