At the northwestern foot of Mount Fuji, on the Yamanashi side, lies the primeval forest of Aokigahara Jukai, spreading across 30 square kilometers. Within this sea of trees, there is an artificial structure.

This man-made structure is an endlessly continuing stone wall, and as you proceed farther in, it reaches a height of as much as 180 centimeters.

This stone rampart is, incredibly, 2 kilometers long. It was built in a curved arc.

Though covered in moss, the material of the rampart is lava that flowed from Mount Fuji and then hardened. This stone rampart has remained shrouded in mystery to this day.

But there is one more “mystery.”

The stone rampart is arranged in an arc, but there’s a place which has a crank shape.