On the Halloween night, I saw Viet wearing the Masked Rider costume and eating a whole box of chocolates.
Ah, you startled me! Why are you wearing that mask?
My dream is to go to the masquerade in Venice and meet a knight on a white horse.
A temporary face is something you put over your face to cover it. It's a mask.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.