The story is fine, I give it that. But neither of the main characters is a saint like some keep saying. Yes, Sori was bad in Chapter 19, and Iseul keeps abusing Soris affection. Might be a hot take, it's just my opinion.
Just because Iseul is in pain, it still doesn't excuse the way she treats Sori half of the time, taking advantage of her, forcing intimacy etc. If I have to pick, I am on Sori's side in this story.