Her parents basically lied to her. In actuality, Rie (the pretty girl from the beginning) was born alongside her twin sister Keiko (the ugly one). Around 14 or so, Rie killed her sister since she became all sorts of paranoid that she was going end up looking like her and losin all her prettiness or whatever. Their parents basically erased all evidence of her sister ever existing and raised Rie as a only kid till she remembered her sister’s existence.
@mootmar thanks for the explanation and but i already understand that
It's just, why did her father look at her (when she hum and twirl around) like that?
It's like her dad's feeling guilty
Or he thinks that her daughter is psychopath, sicko, etc
I like this one. Thought it was going to be another instance of ugly = bad in Itou, but the final twist, wow. Works really well as an horror story, the real monster being the cute MC. And the final page is poweful.
Mostly this. The unsettling part of the ending is that after finding out she murdered her own sister she immediately becomes happy knowing that she isn't going to become ugly and starts dancing in front of the mirror for this