The @Hida Magnesium Mine (飛騨マグネシウム鉱山) is a sprawling, abandoned mining complex carved into the western ridge of the Hida mountains, about 30–40 minutes by foot or vehicle from the village edge along a paved service road. Opened in the early 1920s during the Taishō period, it became one of the largest magnesium extraction sites in Japan by the 1930s, supplying wartime industries with lightweight alloys for aircraft and munitions. Peak operation ran through the 1950s–1960s, employing hundreds of workers from Yomiyama and surrounding hamlets. The mine produced high-purity magnesium ore from deep shafts and open pits, processed in on-site kilns that belched white smoke visible from the village for decades.
1923: Mine opens under private ownership; initial small-scale extraction.
1937–1945: Nationalized during wartime; forced labor used, including Korean and Chinese workers. Production peaks.
August 1945: B-29 crash scatters debris across ridge; some wreckage recovered near mine entrance (including rumored “stone box”).
1946–1971: Postwar boom; largest employer in region. Workers like Sone Takeshi (foreman, died 1971) and @Kumakura Genzō (熊倉 源三) (blaster since 1926) spent lifetimes underground.
1971: Partial tunnel flood caused by a miscalculated blast set by @Kumakura Genzō (熊倉 源三) —wrong moisture reading led to collapse and flooding, killing foreman Takeshi and several others. Genzō carried the guilt; Takeshi's widow @Sone Reiko (曽根 礼子) used his severance to open Kurohi bar in '68, while friend Tatsumi (hungover that day) regretted not being there.
1979: Catastrophic roof collapse kills 12 miners (including @Yamamoto Kōji (山本 浩二) best friend). Mine closed permanently, deemed unsafe.
1986–1987: Fanatics gain town hall approval to reopen usable sections as long-term storage for food and supplies, on the condition they do not disturb the memorial area containing the miners' remains. Trucks made treks up the road, unloading crates into the main shaft @Yamamoto Kōji (山本 浩二) noticed them from his car, thinking the mine was reopening for work. Activity stopped with the blizzard.
The service road is snow-choked, barely passable. Trucks have not come since the loop began. The main shaft is accessible but dark beyond the first 200 meters. The memorial area near the entrance is cordoned off with red rope and a stone plaque listing the dead from the 1971 flood and 1979 collapse. @Yamamoto Kōji (山本 浩二) (museum janitor, 60) visits often, parking his car overlooking the entrance to drink and reminisce about his lost friend. He has spotted supply trucks going in and out of the mine in the months before the blizzard, with people in cultist robes walking the perimeter, looking jumpy and watchful, as if they could see something staring back from the woods around the mine. @Maruyoshi Ryūji (丸吉 隆二) ( @Maruyoshi Supermarket (丸吉スーパー) owner) has been smuggling supplies into the shelter to stockpile for himself and a post-loop world, should one ever come. Kōji keeps quiet about it, but the sight of robed figures and the trucks has left him uneasy.
Faint tremors at 11:55 p.m., like distant machinery.
Whispers of hammering or voices from sealed shafts.
Fresh tire tracks appear on the road overnight, then vanish.
Old mine lamps sometimes turn on by themselves, glowing blue.
Footprints lead into the main shaft and stop abruptly.
The mine is a silent witness to the village’s past—war, labor, flood, collapse, and now something older. It promises answers, supplies, or salvation, but the deeper you go, the more the mountain seems to remember you.