ばけのかわ
mask (concealing one's true character); disguise; sheep's clothing
Also written 化の皮
Expression, Noun
ついに化ばけの皮かわを剥むいだ。
Finally he showed his true colours.
彼かれの化ばけの皮かわをはごうとしたが、むりだった。
I tried in vain to catch him out.