Despite being considered a remote location, it's not that far from Omachi Station by car. You can park your car in the large parking lot in front of Nanokura Sanso (mountain lodge) and take a taxi from the taxi stand in front of Nanokura Sanso to the dam. If you specify your return time, a taxi will be waiting for you. After walking through the long tunnel from the dam's entrance, you can enjoy spectacular views of the Takase Valley and the Northern Alps.
However, the tunnel is long and dark, and there is traffic from dam personnel's vehicles, so it is recommended to bring a flashlight.
This is a truly remote area. It's accessible only by authorized taxis, and there's a dam there. The dam's walls are made of stacked stones, a rare type. Once you pass through the tunnel, you'll come across a suspension bridge and enjoy the spectacular views.