In the mega metropolis of Tokyo, this is about as far west as one can wander.
And, perhaps appropriately, this enormous mass of water is man-made. The Ogouchi Dam, as it is known, stoically holding back a staggering capacity of 185,400,000 cubic meters of water — enough to supply the whole of Tokyo for a full 40 days.
A figure that makes it the biggest reservoir, used solely as part of the water system, in the whole of Japan. Which is fascinating stuff I’m sure you’ll agree.
However, should the dam encounter difficulties, and you happen to be rather dangerously positioned down stream, sirens will sound alerting you of the oncoming deluge, allowing two particular courses of action: either calmly assess the situation and then sensibly seek protection,
or, sensing the seriousness of the sirens, simply panic.