Maruyama Dam near Yaotsu in Gifu opened in 1955 after over a decade of construction which was delayed by World War II. The area is a high-risk zone due to the poor safety precautions to prevent people from falling into the dam; visitors often complain of the low fences and the probable chances of slipping and falling to their deaths. It is rumoured that over a hundred people have fallen into the dam since its construction.
As well as having low safety, the area is frequented by suspicious individuals; particularly, the dam and woodlands are often used to abandon copses. A famous case of corpse abandonment reached news headlines in 2001 when an art deal collapsed and a corpse of a man was found floating in the dam. Due to several bodies being found downstream (including a deceased baby), there are warnings not to venture near the area at night.
Due to the height of the dam and sturdiness of the structure, hanging and jumping suicides are common. A famous rumour exists of a mother who jumped from the pedestrian bridge into the dam with her two children. It is said the spirit of the woman can be seen wandering the area, and people have fled in fear after spotting a child glaring from the tree line. In particular, the maintenance building located to the left of the dam is said to be a hot spot for the woman's face to appear.
Located near the dam is a tunnel referred to as 'Korean Tunnel' due to the use of forced labour of Korean people during World War II. In conjunction to a high death toll, it is reported hitobashira (human sacrifice to reinforce the walls) was a common occurrence. The remains of the people used for hitobashira have not been removed from the tunnel, and access is strictly prohibited due to the high risk of collapse.