(Bake no kawa ga hagareru; “The changeling skin is stripped away”)
Someone’s wrongdoings, flaws, or malicious true nature come to light. A previously-hidden, negative truth is revealed. Someone (or everyone) realizes how bad a situation actually is after a time during which the reality of it was obscured.
We begin with the verb 化ける (bakeru), “to change shape,” especially in the sense of various spirits and creatures that are said to be able to take the form of a human being. This appears in conjunctive form and acts as a noun, which allows the associative particle の (no) to connect it with, and thus modify, the noun 皮 (kawa), “skin,” which in turn is marked by the particle が (ga) as the subject. The predicate this subject takes consists entirely of the verb 剥がれる (hagareru), “to come off (of something).”
Supposedly this comes to us from the 『太平記』(Taiheiki), a 600-some-year-old historical epic.
Japanese mythology is full of shapeshifters, most famously tanuki and foxes from the natural world, to the point where 化け物 (bakemono, literally “thing that transforms”) is used in almost exactly the same way that we use “monster” in contemporary English. Several of the myths even include a special pelt or garment that must be worn or taken off to effect the change.
In keeping with the prominence of animal bakemono, there are synonymous sayings such as 尻尾を出す (shippo wo dasu, “sticking out one’s tail”) that refer to tails – supposedly the one part of the body that a tanuki or fox couldn’t transform, which would expose their true nature if discovered.
(“Jibun no bake no kawa ga itsuka hagarete shimau nja nai ka tte nayande urusakatta kouhai ga shiai de kanpai shite shimatte saakuru wo yameta nda yo ne. Hontou ni nisemono datta no ka, inposutaa shoukougun ni yarareta no ka wa fumei.”)
[“Yeah, the junior member who had been loudly worrying that sooner or later the awful truth about them would be revealed? They were annihilated at the competition, and quit the club. But it’s not clear whether they were really a fake, or whether they were done in by imposter syndrome.”]