As it suggests, this tag is to be used when the protagonist, who is originally described to be ugly by the author, becomes beautiful later on. These adjectives are used for the external physical appearances only. Tag describes the transition of the protagonist ONLY.
I fell in love. Her name was Shirasaki Yukino. I could only look at her from a distance. However one day I heard that she already had a boyfriend. Even if I love her, I can’t have her. The devil sent me an invitation. I can make her mine!