Nexpo.
He does get some pretty obvious things wrong like the Japanese language does not have an emphasis on pronouns, translations often miss that.
The "save me" could also mean "save us", who knows.
This is one of the few really bizarre cases, it's pretty creepy as well. Either another person died or they got out and went on with their lives, fucked.
Or the thing was there before the Kenji guy arrived, then who made it and why?
It could just all be a dumb coincidence. Someone/group built the sign for fun, this Kenji guy got trapped there and stumbled upon the sign so he decided it might be a good spot to wait for help which never came.
Hell, crop circles became a popular troll in the 1980s, which does coincide with this guy done goofed.
Crop circles was a thing and it was made by 2 bored artist dudes with wooden planks and ropes which should have always been obvious from the get-go.