I'm not the only one tired of the, mother never notices how obviously deceitful and manipulative the female villain is, trope right? It's so fucking obvious!
There was no consent from either character. Frankly I wouldn't be surprised if Chiwoo was messed up in his own way and the author just hasn't shown us yet.
The sister seems to be just a filler character. Just there to be there and cause drama. Unless she plays a big role later on in the story she's pretty much an unnecessary and useless character. I personally don't like her.
Talk about a clusterfuck! XD