When you meet her, she seems really cold, calm, and extremely quiet, but if you become a really close friend, she's actually rather hyper and loud. Unfortunately, you have to be an EXTREMELY close friend for her to act this way. When she's by herself in front of strangers or a large crowd it's as if she's lost all train of thought. Basically, she has a huge case of stage fright in front of people/strangers; it's even worse if she's put into the spotlight in front of a crowd. Similarly, no one knows she's hyper or loud at all; though most people usually come to the conclusion that she’s either mysterious or stuck-up. Ask any friend of hers and they'll tell you people always ask why Sungjin is so quiet while the friend just sheepishly smiles knowing it's no use explaining. Also, she tends to settle with "behind-the-scenes" work, many times letting other people take the credit for her hard work. However, one of her strongest points is her observation skills in which she is very precise when assessing a person or situation.

Still, her shyness is definitely a problem. In addition, she is the farthest from being a risk-taker. Those two qualities combined becomes pretty disabling for her. She still has a lot to show—she has very unique ideas and is quite the master with words—but her lack of boldness and confidence obviously fails her. Also, despite her age, and having never been in a relationship before, she’s a great old sister type who gives great advice—so much so, that sometimes people mistake her for being older because of her “wise” life and relationship advice.

Besides her flaws, she does have accompanying strong qualities about her: loyalty and trust. Some might say she is just innocent in this aspect, but she believes everyone is a decent person upon first meeting, giving everyone she meets the same level of her trust. This level of trust is her basic, scratch of the surface, guarded trust (as in she doesn't believe you're out to get her, or you have a reason to lie to her when giving her facts, but guarded in the sense that she will rarely tell you much about her). However, when you gain her trust, which is quite difficult to obtain (that guarded part is rather strong), she becomes an extremely loyal friend. Still, if you give her one clear action of doubt, that trust she has given you shatters, extreme loyalty gone...she can drop you off her friend list like a hot potato.

Even though she’s great at hiding what she really feels, and though people compliment her on her great ability of acting naturally, Sungjin has a playfully short temper. Although she likes to make facial expressions, she’s really good at controlling them. For example, have a “Who-Smiles-First-is-the-Loser-Contest”, and you’ll lose hands down. I must warn you though: uses sarcasm/witty remarks; extremely stubborn when she wants things to go her way; she can be a rather bitter, negative person in a semi-evil way. Lastly, she's a very realistic girl...not the type to believe in fairy tales; sure she daydreams and has a very creative mind, but when it comes to viewing the real world and her future, she's not the type think her life is that of a fairytale princess.