No way bro.
That "Japanese" must've been Chinese or some other Oriental language.
And if it was written in Japanese, where were they going to "return" you? The nearest POW camp?
And Steve just said they were used in WW2 w/the AVG.
You do realize that when a country goes to war, not every citizen of that country supports that decision, and may even act in a way contrary to supporting the war effort.
It is quite possible that sympathizers exist among the local populace. They may decide to aid a downed aviator for numerous reason (religion, past positive experiences with "enemy" country, pacifists, just plain nice guy, etc.) Sure, contacting the locals in "enemy" territory would be a last resort, but it sure would be nice if your blood chit was in their language.