Who is the one person you can't fool, no matter what?

Can't fool...no matter what...?

Let's see, "damasenai" means "can't fool," and the "nai" part means "no," so maybe it means something without "da," "ma," or "se" in it?

If I remove those letters from a word, then... No, maybe it's a person who doesn't have any of those letters in their name...?

Heehee.

Was it a little too hard for you?