Japan has a notoriously high suicide rate, which doesn't seem entirely justified considering it's 10th in the world, with south korea for example being 50% worse.
This forest was always shifty, but its popularity grew due to a contraversial book, The Complete Manual of Suicide where it is described as the perfect place to die. Over 100 bodies per year are discovered there, a lot more probably don't ever get found.
I don't want to repeat things too much, vice has a good 20 minute documentary on it.
To make things comically creepy, the forest lies on some large magnetic rocks, which make compasses useless. my gps seems to rely on a digital compass, so I quickly rehersed the night before on how to orientate myself by the sun.
The place is fairly touristic, it has a few hiking trails, and it lies just below mount Fuji. When we got there they told us that a black bear was sighted today exactly where we were going. We ended up yelling and clapping our hands a lot to scare it away. We walked a lot, not knowing exactly where we should go, and got off the trail a lot, relying on a bad tourist map.
A small culture grew around suicides in the forest. for example, people that think that they might change their minds, walk in leaving a trail of (usually nylon) string, which makes parts of the forest look really strange, with nylon strings going everywhere. The whole place is full of strange objects that seem to have been used in ritual like situations. Compass and gps ended up working well for the most part, with occasional crazyness.