At present, the scope of the scientific expedition team's survey was still within the region of Mount Fuji. The rainy season brought severe high tides, and the surging Tama River flowed mightily past the side of their campsite, its waters spilling far over the riverbed with a strong tendency to flood.
Deep beneath their feet flowed an undercurrent known as the Red Oni River. Unlike ordinary cold and gloomy subterranean rivers, part of the Red Oni River originated from the magma at the foot of Mount Fuji. The scorching heat of the magma turned the source of the Red Oni River into boiling water. When it met the freezing Tama River somewhere in the valley, the blending of hot water and cold springs produced a tremendous roar. This sound, reflected by the valley, echoed like thunder crashing at the bottom of the gorge, which was why this place was also called Thunder Valley.
Legend had it that Thunder Valley was a place the Yamata no Orochi had visited. One of the heads of the Yamata no Orochi had once drunk the water in the Tama River dry, whereupon it let out a deafening roar. The sound summoned thunder from the sky to strike this valley, and this was the origin of Thunder Valley in mythological history. The local people firmly believed this statement, because there was a giant lightning-struck tree in the valley, and around this tree, an ancient Yamata Shrine had been built. According to legend, this shrine had stood in this valley since the Nara era.
Chapter 450