Lost Woods
The Lost Woods is a deep, perpetually dark evergreen forest on the southern slope of Engetsu-san. In fact, it's so well enclosed with tree cover, that navigating the forest itself can be nigh-impossible, as one is left with no directional references. The presence of powerful ley lines running through the area has the added problem of interfering with technological and magical mapping, leaving it an area best left alone by all but the most determined of explorers.
None the less, there persist rumors of an ancient, abandoned shrine hidden deep within the woods, which inspires the eager and foolhardy to try exploring it despite the warnings. Few are stubborn or determined enough to make their way through, but it's apparently enough to continue to inspire many to take their chances with the dark, forboding wood.