In the summer of 864 CE, during the sixth year of the Jogan era, Mount Fuji erupted from a vent called Nagaoyama on its northwestern flank. The eruption was both explosive and effusive, pouring enormous quantities of lava down the mountainside. The flows reshaped the geography permanently: an ancient body of water called Lake Senoumi was split in two, creating what are now Lake Saiko and Lake Shojiko, two of the Fuji Five Lakes. The lava field solidified into a vast, porous platform, and over the following centuries, a forest of cypress, hemlock, and other conifers took root in its cracks and hollows. Because so little soil has accumulated on the rock, the trees grow in strange, exposed configurations, their roots weaving across the surface like gnarled fingers.

The western edge of Aokigahara is the most visited, and for good reason. Here, the lava field's natural chambers and tunnels have become popular tourist destinations: the Narusawa Ice Cave stays frozen year-round, the Fugaku Wind Cave offers a different underground experience, and the Lake Sai Bat Cave rounds out a trio of accessible lava tubes. Above ground, Aokigahara sustains a surprisingly rich temperate ecosystem. Asiatic black bears den in the forest. Dsinezumi shrews and small Japanese moles navigate the root-laced floor. The canopy shelters great spotted and Japanese pygmy woodpeckers, Eurasian jays, Japanese grosbeaks, and Siberian thrushes. The dominant tree species shifts with altitude: Tsuga diversifolia hemlock prevails between 1,000 and 1,800 meters, giving way to Abies veitchii fir above that.

Aokigahara has long carried a reputation as a haunted place. In Japanese folklore, the forest is said to be inhabited by yurei -- restless spirits of the dead. Some accounts link this belief to the practice of ubasute, in which elderly or infirm family members were allegedly abandoned in remote areas during times of famine, though the historical reality of this practice is debated. What is not debated is the forest's modern association with suicide, which has been documented since at least the 1960s. Signs posted at trailheads urge visitors to reconsider and provide contact information for crisis support services. The association intensified after Seicho Matsumoto's 1961 novel Nami no To (Tower of Waves) featured the forest, though the pattern clearly predates the book.

Aokigahara's notoriety has sometimes overshadowed its genuine ecological and geological significance. This is a forest that grew on a lava field in just over a millennium -- a vivid demonstration of how life reclaims even the most hostile terrain. School groups visit the ice caves. Hikers follow designated trails through cathedral-quiet stands of hemlock. Naturalists come for the birdwatching. The deeper reaches of the forest host herbaceous and flowering plants, including Artemisia princeps, thriving in the sheltered gaps between lava formations. From above, Aokigahara appears as a dark, unbroken canopy pressing against the northwestern base of Fuji, bordered by Lake Saiko to the north and Lake Shojiko to the west -- the same lakes that the eruption created, now framing the forest it left behind.