Opening in 1970 after beginning construction in 1962, Yahagi Dam (矢作ダム) is a one-hundred metre concrete structure located near Takanosu Mountain. Built to prevent flooding from the man-made Okuyahagi Lake, Yahagi Dam is a local treasure due to its natural landscape, colourful trees in the changing seasons, and abundant fishing.
Despite its green scenery and fishing spots, Yahagi Dam and Okuyahagi Lake are hotspots for people to commit suicide. Opposite to Okuyahagi Lake, Yahagi Dam has a steep drop which a number of people jump from each year. Along the bridge which connects the east side of the dam to the west, bouquets of flowers often line the pedestrian path; symbolising the loss of a loved one due to suicide.
Okuyahagi Lake also has a number of incidences involving drowning in which the bloated bodies wash ashore among the thick shrubbery. There is a report of a driver parking their car along the red bridge before setting themselves and their vehicle aflame in order to take their life.
There are claims that venturing near the dam or lake at night causes a sense of uneasiness, sorrow, and being watched.
According to Japanese social media, the tunnel located on the east side of the dam next to the resting area is believed to be haunted by a malicious entity. Drivers have told of instances in which they assist female hitch-hikers, only to meet a grizzly fate at the final destination.