Childishness in adults is not a Korean only thing.Some people grow up not knowing how to deal with certain situations and they still consider childish behaviors a safe and acceptable reaction. Adult by law doesn't mean that person consciously becomes an adult.   See 4 other replies

And I'm talking about Hyo Sun of course. Moon (Eun Jo) looks fine.   See 5 other replies

I didn't notice until she started crying in Ep 2 and they showed more portions of her face from the front. She looks malnourished and ill.   See 5 other replies

The director himself noted that he chose Seo Woo for this role bc she can act overly childlish and not make the audience turned the tv off. (It's hard not to b sooo innocent and make people tolerate it). The more childlish and innocent Hyo Seon is at the point when she was young, the more people can see the "change" in her personality when she grows up, also it makes Eun Jo's personality be even more distinguished. (like in American movie, to make 2 main leading ladies b different from each other, they would cast actresses like blonde and brunette, boyish and girly girl, tough and fragile)...
Having said that, they have to make Hyo Seon looks like a girl who comes out of an unreal world where everything is just... unreal. (well i mean except the fact her mom dies when she was 7, her dad's rich, she is the princess, the got a great guy with her)... I think the crew did a good job making her looking like that   See 1 other reply

Eun Jo thought Chang was going to try and do something to her in her mother's absence. (Sexual abuse) To the statement above about the posture with the hands over the head its a disciplinary thing that our ancestors had to do and it's just gone through that generations. You raise your arms over your head and sit on your knees. the longer you stay like that the more blood rushes away from your limbs and the pain from holding your hands up over time becomes excruciating. No matter what your not allowed to drop your arms till you're told to. They can also whip the bottom of your feet with bamboo saplings and make you hold up buckets of water while your doing it. If your move while being punished it just gets worse and you have to start all over again. Some believed it was a way to detach your mind from your physical pain and learn self control and pain tolerance for later in life. This was mostly practiced a long time ago but the meaning behind it is understood from the elders. It's now a way of showing remorse.   See 4 other replies