I think that may be Acadia National Park. A few years back I took a pic of a nearly identical sign at Sand Beach. Sent pic to a few friends with a text "Not quite what I was expecting but still fun."
I've never been to Japan but I have been to Bataan (think "Death March") and Corregidor Island in the 60's which still had machine gun slugs rolling around in the surf.
Even at a young age I felt the weight & somber presence of death that permeated those places.