The Aokigahara Forest is located to the north of Mount Fuji, which grew over the lava bedrock following the volcano's last major eruption in the 9th century. The dense forest is known as the "Sea of Trees" given the quiet and sparse territory found here. A number of caves, like the Narusawa Ice Cave and Fugaku Wind Cave, can also be found here.
Aokigahara Forest has an unfortunate reputation as a destination for those struggling in their lives — if this describes you, please consider talking to someone.
The nearest station is Kawaguchiko Station on the Fuji Kyuko Line (around 2 hours from Tokyo).
From there it is a 30 minute drive west along Route 139 and 71.