Reading the dialog, all the things that the guardians are afraid of; power, anger and dark forces all point to the light of a dragon in the sky. And on the sign, the flying dragon is depicted in the bottom or south side. That's as far as I can get... I can only guess the other three must be a clue as to where the statues are... but that doesn't make sense to me since technically, two are on the right side from where the sign / door is. If I knew Japanese, I'd ask on the forum... I may just try anyway and hope I'm understood. lol