Yamanashi’s landscape holds a darkness that its tourist brochures do not advertise. The same volcanic mountain that appears on calendars and banknotes is, in Japanese folk tradition, intimately connected with the boundary between the living and the dead. The forest that grew across its lava field after the eruption of 864 AD absorbs sound and disorients navigation; the mountain’s traditional ascent route begins with a purification ritual designed to protect climbers from supernatural harm; and the valley east of the crater has been understood in Japanese religious culture as a portal to the underworld since the Heian period. Yamanashi’s mysterious places are not manufactured attractions — they are part of an ancient landscape that has always been understood as existing on the edge of the known world.
Aokigahara Jukai: The Sea of Trees
Aokigahara is the most famous and most mysterious forest in Japan. Growing across the 35-square-kilometre lava field produced by Mt Fuji’s 864 AD eruption, the forest is distinguished by characteristics that are simultaneously geological and uncanny: the dense root system growing over jagged lava creates an eerie, silent environment where animal life is scarce, where sound is absorbed rather than reflected, and where the magnetic iron content of the underlying rock causes compass needles to behave erratically.
In Japanese folklore, Aokigahara has been associated with yurei (spirits of the dead) since at least the Edo period. The forest was understood as a place where the dead returned — a liminal zone at the foot of a sacred mountain where the membrane between the world of the living and the realm of the dead was thin. The tradition of ubasute — leaving the elderly in mountain forests in times of famine — is historically associated with this area.
Walking the marked trails within Aokigahara during daylight hours is an entirely accessible and deeply atmospheric experience. The forest has a quality of silence and density that is difficult to describe: the canopy filters light to a dim green, the ground underfoot is irregular lava rock partially hidden by moss and fallen branches, and the absence of bird sound creates an unsettling quiet. Stay on the marked trails and return well before sunset.
Access: The main trailhead near the Fugaku Wind Cave is accessible by bus from Kawaguchiko. The forest trail is marked and easy to navigate on the main path.
Narusawa Ice Cave: Cold and Dark Beneath the Mountain
The Narusawa Ice Cave is a lava tube — a tunnel formed when the outer surface of a lava flow cooled and solidified while molten rock drained from within. Inside, year-round temperatures remain near 0°C, and the walls and ceiling accumulate ice formations in the colder months that persist well into summer. The combination of the narrow passage, the low temperature, the coloured lighting, and the irregular ice-covered rock creates an environment that registers as genuinely otherworldly to most visitors.
The cave was historically understood as a passage into the earth’s interior — associated in Shinto cosmology with the realm of Yomi, the underworld. The proximity to Aokigahara and to the Fuji lava plain amplifies this atmosphere: this is a cold, dark hole at the foot of a sacred mountain, inside a forest associated with the dead.
The cave is open to tourists (entry ¥350), requires a short crawl in one section, and is suitable for most visitors in good health. Bring a warm layer and solid footwear.
The Lost Village of Nenba (Saiko Iyashi-no-Sato)
At the western end of Saiko Lake, the village of Nenba was buried under volcanic debris when Mt Fuji erupted in 864 AD. The entire community was entombed beneath the lava and ash — houses, fields, people, animals. The village was excavated centuries later and the site reconstructed as the folk museum Saiko Iyashi-no-Sato, but the knowledge that the ground beneath the thatched farmhouses conceals the remains of an entire buried community gives the site an atmosphere beyond ordinary heritage tourism.
On grey days in late autumn or winter, when mist moves through the thatched rooftops and the surrounding Aokigahara forest presses close, the site has a quality of suspension — as if caught between what it was and what happened to it — that is unusual among tourist destinations and entirely understandable.
The Supernatural Folklore of Mt Fuji
In Japanese religious tradition, Mt Fuji is simultaneously the dwelling place of the mountain goddess Konohanasakuya-hime and the location of one of the entrances to the Buddhist underworld. The summit crater, the interior of the mountain, and particularly the northeastern forest zone have been associated in folk belief with the realm of the dead for over a thousand years.
The Yoshida Trail’s starting point at Kitaguchi Hongu Fuji Sengen Shrine involves a ritual purification — historically understood as protection against the supernatural dangers of ascending a mountain that exists partially in the divine world. Climbers who die on Fuji in the folk tradition are understood to continue their ascent in spirit after death.
Practical Notes for Mysterious Yamanashi
Aokigahara can only be explored safely on marked trails in daylight. The forest is large enough that going off-trail poses genuine navigation risks independent of any supernatural consideration.
The Narusawa Ice Cave is tourist-accessible but requires appropriate footwear — the floor is uneven ice-covered lava rock.
The Saiko Iyashi-no-Sato is open daily, entry ¥500. The atmosphere is at its most powerful in late October and November, when mist is common in the valley and the surrounding forest is in autumn colour.