expression, ichidan verb
to betray oneself; to reveal one's true colors; to give oneself away
Idiomatic expression meaning that a person's hidden true nature or intentions are exposed, often after a pretense. Literally 'the skin of a disguise is peeled off'.
See also: 化けの皮
His kind attitude was a lie, and his true colors were soon revealed.
あの政治家は、汚職が発覚して化けの皮が剥がれた。
That politician's true nature was exposed when the corruption came to light.